For flipping or wholesaling, we buy based on being able to meet enough profit for the price point to make it worth our while based on the total investment required for purchase, holding, rehab and sale.

Think of all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

A live in flip/rehab? 

I’ve always been the kind of guy that does everything myself, and have alreadu done all the work required for full gut rehabs myself at some point (and have taken one project all the way through).

Does anyone know the legality and ethics of registering at a rental address?

In the Cambridge-Somerville area, triple deckers in need of repair easily go for multi-millions, you need a lot of capital upfront for downpayment and rehab costs and you are relying on appreciation to build equity - the flip and condo conversion is a popular option in these areas. 

And rehab and treatment of back willbe more expensive than not having a job.

Upon completion of rehab, or once tenanted with a lease is ideal. 

She owns the house free and clear.We have a lawyer.I figured this is a great opportunity for me to possibly rehab and cash out refi for leverage to re invest?

I volunteered one of my rehab projects but it was at the same time that someone else volunteered their rehab project just a few miles from my RE so the other rehab effort was used.