You should always look for Tax-Deferred and Tax-free methods to Invest.

Often times when a builder/buyer moves too fast, or is too busy and overlooks a key piece of due diligence, the unethical ones will try the "scorched earth" method and blame everyone but themselves, even when they know it was their own mistake, and they'll see if they can scare you, the seller, the title company et al into paying damages/fixing their problem. 

Then Joe sends a letter to Bob and says I bought your mortgage make payments to me.

How much are you short for the down payment?

Think about it, if you are buying something at a 5% cap rate, but interest rates are 6%, the debt payment exceeds the income.

Are there specific methods you're interested in (BRRRRs, vacation rentals, flips, etc)? 

What is the repayment schedule (monthly interest-only, balloon payment, etc.)?

I turn to them to list the rental, which just means another form of payment for them. 

I mainly want a site that offers advertising the property, online payment options, maintenance requests & at least a basic accounting aspect.Thank you in advance!

(Down Payment Assitance Program).