Review their management agreement.

As long as everyone is able to eat and everyone agrees to the terms with transparency, this type of agreement shouldn't be negative. 

Since we first signed a 1 year lease agreement 3 years ago, the owner has expressed wanting to sell to us, or that we would be the last tenants she has in the home.

Since we first signed a 1 year lease agreement 3 years ago, the owner has expressed wanting to sell to us, or that we would be the last tenants she has in the home.

Since we first signed a 1 year lease agreement 3 years ago, the owner has expressed wanting to sell to us, or that we would be the last tenants she has in the home.

When we agreed to the deal for $340 per month when we do business we intend to honor our agreement through thick or thin and through any hardships we incur.

Then you can use your hybrid sale/rental/CD agreement to charge FMV rents, because we all know a tenant will not pay more. 

Normally I would add both on the lease agreement equally responsible for it, but in this case can I specify that the original tenant is the primary tenant responsible for all financial side of the agreement?

Any EMD would go direct to escrow and then and only then once I have reviewed and agreed to the purchase contract and any and all terms enclosed in it such as inspection timeframe, closing, purchase price, who pays what closing costs, etc.Your due diligence must happen prior to accepting the wholesalers contract unless you also are granted an inspection period inside the purchase agreement with the seller.Everything is negotiable so if the price from wholesaler to you is too high, negotiate it down.

Or should I set on a final sale price and a separate lease agreement for the monthly rent?