If you move in, or alter anything even, prior to closing they will cancel your contract. 

My original impression of rent to own was that it’s the same as regular rental, but with a buy date and additional funds being given as option fee.

Well, if you bought a car the day after closing it would appear you Applied for the loan at least before closing of the loan which would violate documents you sign at closing, with the lender, saying you are not applying for additional debt. 

I have about $14000 additional  cash to begin the rehab but that wont get me far as the furnace/air/duct work alone will cost $11000. 

Additionally when the markets do turn you will lose all your equity and be back to earning 1-200 per door per month. 

My lender also ask for additional comps to be added and to have it reviewed again.

I'd second the 'meet with a commercial lender' and 'driving for dollars, knocking on doors and direct marketing comments'.A couple additional thoughts.First, even though I appreciate the ambition , there is also nothing wrong with going slow.

I have bought from a family trust before and in addition they sold the other 4 to me!

This will come at additional cost from what I was originally quoted.

Always include in your lease that tenants are not permitted to alter the unit in any way and when you are reviewing your lease with new tenants always highlight this clause.