I agree with @Michael Carbonare:  specify the lease terms and the purchase terms.In one deal I did, we agree upon the purchase price, lease amount, and a nonrefundable deposit towards the purchase. 

@Eric BarriosAlways get an estoppel signed by the prior owner an all tenants regarding lease agreement specifics, security deposit held and amount paid or outstanding.There are countless stories of new owner finding out from tenants after the fact a different stories than what was told by the prior owner before the sale.

Saves you a lot of time.Then once they find properties that match your goal monthly returns, you can check their work.As far as the condition of the property, it depends on how much cash on hand you have to potentially do any renovations.

Factor in the possible replacement/repair costs and if the numbers still work out, the property matches your crystal clear criteria, and it looks like it will be a strong profitable deal, then take the next step - Otherwise, let it go.

@Chey ZwickerConfirm verbally that the tenants have been paying on time and then ask for bank statements showing the deposits before accepting the tenants. 

Recently, he mentioned he will be leaving and wanted to see if he could only pay 3200 and I could take off 2 months worth of rent and keep the 500$ deposit .

If they were two options: delay closing for 1 month and make sure the one tenant is out or remind them that they were served notice and have to move by the end of the month.Hopefully you are getting the deposit of the other tenant transferred at closing along with prorated rent.

The owners are selling otherwise they would have stayed longer.How much would you deduct from their security deposit for these two floor scratches? 

If not, tell the tenants they can take a tiny slice from the wall (paint only) and if they take it to one of the big box stores, it can be matched so they can pick up a sample to do the touch up. 

All the while, you haven't invested much money, given you're likely to pay an initial deposit, and not begin paying a mortgage until the construction completes.