I have since done a complete rehab with new kitchen and bathroom, high end carpet in the bed rooms, porcelain tile in all other house space, deck install and all new appliances.

This would require you to have a solid business plan and property analysis in place to get them to say yes, but you could buy properties with their cash and pay them back in installments at a percentage you decide.

The original walls of the house were not plaster and lath as I suspected but actually homasote (or something very similar) with wall paper installed over it.

I had little leverage because I wasn't holding the last installment of their payment like I would have been if we had priced on a project basis opposed to a project basis.Get everything you want completed clearing outline in a statement of work and have them bid the job.  

I  believe it will need basic cosmetics including paint and carpets removed/flooring installed considering it has been a rental.Your advice is appreciated!

I have seen some bad stories about leasing coin op machines, you might try searching for threads about it here on BP.If you manage your rental yourself or you have a PM you trust, it is easy to collect the coins every month or so.If your rental is in a questionable or hidden area, I would recommend getting the coin vault guards installed to prevent damage from tampering.

In secondary bathrooms, shower/tub combo or 6' tile/glass shower?  

Yes, we installed a new dark charcoal nearly black roof on this house which coordinated well with the gray, black shutters and black entry door.I am also a little stumped

I will also need a surround so would do tiling if PoS or a matching Acrylic surround if I choose an Acrylic tub. 

I want you to have legal advice and be comfortable with this decision about your home.Now I will tell you, unless your attorney is an expert and lease with option, subject to existing financing, owner financing, and other legal remedies for your situation, he's probably have a say don't do it.Then I reach for my nolo.com article, and go over the different seller financing possibilities.And I walk them through all the situations, from lease purchase to subject to installment sale to wraparound mortgage."