There is no limit on digital mode receipts & payment. But there are certain restrictions on cash payments & receipts. Like –

• Section 269ST prohibits a person to receive an amount of Rs. 200000/- or more in cash from a person in a day in respect of a single transaction.
• Section 269SS & 269T prohibit a person to accept or repay loan and advance of Rs. 20000/- or more in cash.
• Section 40A(3), disallow the expenditure (in PGBP) which is paid in cash. 
• Higher audit limit u/s 44AB, for business not more than 5% of receipts and payment are in cash. (hence more than 95% receipts and payments transaction should be through banking channel or digital mode.)
• Section 44AD, provides for less presumptive income i.e. income shall be computed at the rate of 6% instead of 8% if turnover/gross receipt is received by an account payee cheque or an account payee bank draft or use of electronic clearing system through a bank account or through such other electronic mode.

Restrictions on cash transactions can be summarised as follows:-

1. Section 269ST:– No person shall receive an amount of Rs. 200000/- or more (a)  in aggregate from a person in a day; or (b)  in respect of a single transaction; or (c)  in respect of transactions relating to one event or occasion from a person, otherwise than by an account payee cheque or an account payee bank draft or use of electronic clearing system through a bank account or through such other electronic mode as may be prescribed. On violation of this section penalty upto 100% of transaction amount may be imposed
   this section shall not apply to  (i)  any receipt by—
    (a) Government;
    (b)  any banking company, post office savings bank or co-operative bank;
   (ii)  transactions of the nature referred to in section 269SS
2. Cash receipts & repayment of loans & advances:- Section 269SS prohibits Cash payment of loans, deposits or any advances for Rs. 20000 or more. and Section 269T prohibits cash repayment of such loans, deposits or advance for Rs. 20000 or more.
   In Short, A person is not allowed to accept or repay any loan, deposits or advances of rs. 20000 or more from another person in cash. But such transaction should be only through an account payee cheque or electronic clearing system like net banking , UPI , BHIM app etc. On violation of these section penalty upto 100% of loan amount may be imposed.
   Provisions of section 269SS & 269T are not attracted if :-
   1. Any loan or deposit or specified sum “taken or accepted from” or “taken or accepted by” the following entities –

   a. The Government
   b. Any banking company, post office savings bank or co-operative bank
   c. Any corporation established by a Central, State or Provincial Act
   d. Any Government company as defined in clause (45) of section 2 of the Companies Act, 2013 (18 of 2013)
   e. Any institution, association or body or class of institutions, associations or bodies notified in Official Gazette

   1. A person earning only agriculture income accepts loan or deposit from  another person also earning only agriculture income (only for 269SS)
   2. Receiving cash from relative during emergencies. Here intention should not be to evade the taxes. ( assessed on case to case basis)
3. Disallow expenses paid in Cash:-  As per section 40A(3), No deducted of expenses shall be allowed for any expenditure in respect of which a payment or aggregate of payments made to a person in a day, otherwise than account payee cheque or account payee bank draft or use of electronic clearing system through a bank account, exceeds Rs 10000 . This limit was 20000 upto FY 2016-17.
   There are some exception of this section 40A(3), exception are given under rule 6DD as given below:-
   These circumstances and cases as provided under Rule 6DD are as follows:
   (a) where the payment is made to—
   (i) the Reserve Bank of India.
   (ii) the State Bank of India or any subsidiary bank.
   (iii) any co-operative bank or land mortgage bank:
   (iv) any primary agricultural credit society or any primary credit society.
   (v) the Life insurance Corporation of’ India
   (b) where the payment is made to the Government and, Under the rules framed by it, such payment is required to be made in legal tender;
   (c) where the payment is made by—
   (i) any letter of credit arrangements through a bank;
   (ii) a mail or telegraphic transfer through a bank;
   (iii) a book adjustment from any account in a bank to any other account in that or any other bank;
   (iv) a bill of exchange made payable only to a bank;
   (v) the use of electronic clearing system through a bank account
   (vi) a credit card;
   (vii) a debit card.
   (d) where the payment is made by way of adjustment against the amount of any liability incurred by the payee for any goods supplied or services rendered by the assessee to such payee;
   (e) where the payment is made for the purchase of-
   (i) agricultural or forest produce; or.
   (ii) the produce of animal husbandry (including livestock, meat, hides and skins) or dairy or poultry farming; or
   (iii) fish or fish products; or
   (iv) the products of horticulture or apiculture, to the cultivator, grower or producer of such articles produce or products;
   (f) where the payment is made for the purchase of the products manufactured or processed without the aid of power in a cottage industry, to the producer of such products;
   (g) where the payment is made in a village or town, which on the date of such payment is not served by any bank, to any person who ordinarily resides, or is carrying on any business, profession or vocation, in any such village or town;
   (h) where any payment is made to an employee of the assessee or the heir of any such employee on or connection with the retirement retrenchment resignation, discharge or death of such employee, on account of gratuity, retrenchment compensation or similar terminal benefit and the aggregate of such sums payable to the employee or his heir does not exceed fifty Thousand rupees;   –
   (i) where the payment is made by an assessee by way of salary to his employee after deducting the income-tax from salary in accordance with the provisions of section 192 of the Act, and when such employee-
   (i) is temporarily posted for a continuous period of fifteen days or more in a place other than his normal place of duty or on a ship and
   (ii) does not maintain any account in any bank at such place or ship;
   (j) where the payment was required to be made on a day on which the banks were closed either on account of holiday or strike;
   (k) where the payment is made by any person to his agent who is required to make payment in cash for goods or services on behalf of such person;
   (l) where the payment is made by an authorised dealer or a money changer against purchase of foreign currency or travelers cheques in the normal course of his business.
4. Impact on Tax audit requirement :  For FY 2022-23, A person carrying on business is required to get his accounts audited by Chartered Accountant, if his total sales, turnover or gross receipts (as the case may be) in business for the year exceed or exceeds Rs. 1 crore.This provision is​ not applicable to the person, who opts for presumptive taxation scheme under section 44AD​ and his total sales or turnover doesn’t exceed Rs. 2 crores). Note: In budget 2021, The threshold limit, for a person carrying on business, is increased from Rs. 1 Crore to Rs. 10 crores in case when cash receipt and payment made during the year do not exceed 5% of total receipt or payment, as the case may be. In other words, more than 95% of business transactions should be done through banking channels.
5. Income under Presumptive taxation (44AD): – For FY 2022-23, If turnover or gross receipts of business do not exceed 2 cr. then assessee can opt for presumptive taxation u/s 44AD. In case of a person adopting the provisions of section 44AD, income is computed on presumptive basis at the rate of 8% of the turnover or gross receipts of the eligible business for the year.In order to promote digital transactions and to encourage small unorganized business to accept digital payments, section 44AD is amended with effect from the assessment year 2017-18 to provide that income shall be computed at the rate of 6% instead of 8% if turnover/gross receipt is received by an account payee cheque or an account payee bank draft or use of electronic clearing system through a bank account or through such other electronic mode as may be prescribed during the previous year or before the due date of filing of return under section 139(1).

In your question, One person is engaged in two businesses, please refer following additiona points in this regard:-I

1. Section 44AB, applies to a person and not only to a specific business hence If you are involved in more than 1 business, you will be liable to audit your accounts if the total turnover of all your businesses taken commulatively, is more than Rs. 1 crore. If you operate more than 1 profession, you have to audit your account books in case the gross receipts of all the professions cumulatively cross Rs. 50 lakh.
2. If you run a business as well as a profession, then tax audit is not based on total turnover from both. If your business turnover is more than Rs. 1 crore then an audit is required for the business accounts, and if the gross receipts from your profession is more than Rs. 50 lakh then an audit of the profession accounts is needed. But if your business turnover is Rs. 95 lakh and your profession receipts are Rs. 45 lakh, then no audit is required for either accounts.