For filling itr 4s

Sir, My client has 2 sources of income. One is salary income i.e Rs. 8,500 /- pm, and 2nd is he has one tata ace which he gives in rent so rent income i.e Rs. 15,000 /- pm approx. Now he wants to declare his income in ITR 4s as presumptive basis of his rent income and shows his salary in this form also which he received in bank account. Now my queries is that - In ITR 4s what he will select as nature of business field in NOB tab although in his trade licence he mention that general order supply and trading business but he done vehicle rent business. So, if he shows trading and other business from list and shows rent income Rs.7,500 /- pm in ITR 4s then any problem will arise from IT dept? Pls clarify me anyone.