.$650k x 70% = $455k$455k - $10k for minimal work = $445k$445k - $7k your desired fee = $438k$438 is the MOST you should pay, and that is assuming very light rehab. 

(Which I will do my best to make sure that there's nothing or if so its minimal) Lastly, once I get a contract with the seller don't I have to open escrow ?

I used to think that having tenants sign longer leases (2+ years) were better than shorter ones (1 year or m2m) to minimize turnover and vacancy, but that's not necessarily the case.

I'm a realtor in Marblehead and can help you and connect you with lenders who will qualify you for a loan with minimal down payment.  

There are specific way to structure it and minimize risk, that's why I'd like to find a local attorney who does these deals on a regular basis.  

This addition is designed as a completely separate unit however it can easily flow into the existing house, creating a 3/2 with minimal work if needed.

Hopefully that would minimize your calls.  

However, as @Andres Verney suggested, if you get a percentage off of other people's rentals, and roll that into your own, that could help you on your way and allow you to minimize the expenses on your own rentals.

:)This house is in Birmingham, AL and I am trying to wholesale the propertyThis house is listed with a realtor on the MLS for $79kARV is about $75k and minimal updates / repairs are necessaryThere is $68k remaining on the loan balance, but the seller is behind a few months on the payments and might have to short sale it to the bank (does this even make sense, I'm not entirely clear how short sales work?)

That's the price you pay for "easy" money with minimal risk (i.e., wholesaling).