@Rahul Handa Your question is a bit vague in that you have not provided much information on your market or your circumstances. So, we will need to make some assumptions. Then you can follow the logic. If the assumptions are not accurate, then change them for your needs and re-run the logic. 1) Based upon deals you have analyzed for your market, how much do you anticipate make per door? If you assume 250/door, you need 10 properties. If you make 100/door, you need 25 properties. 2) Again based upon your market and your analyses of properties, how much does a property cost? For this example, we will assume a $60,000 property will cashflow $250/month. We will also assume you will get conventional loans with 20% down, closing costs are $5000, and flooring/paint cleanup is another $5000. So you will need $22,000 per property (12,000 down +5000 +5000). So for10 properties, you would need $220,000.
However, your mortgage would only be for $48,000. Many lenders will charge $2000-3000 extra for loans less than $50,000. Further, you need to have cash reserves for property management, capex, etc. You have to figure this based upon your risk tolerance.
Also note, you may not be able to get 10 conventional loans, so you may need to get business loans where 25-30% down is required.
Anyway, this should get you started with figuring out how to put a strategy together. Good luck to you.