IMO I think you would have to review both pre and post tax benefits/deteriments as taxes are part of every (legal) financial deal.

Moreover, there are legal reasons that you don't want people working for free.

I know to subtract the land value from purchase price, but do I include: closing costs, seller paid costs, prepaid items.  

If it's all done legally, why would they be able to sue?

I'm just assuming 50% of the rent will go to expenses (taxes, insurance, maintenance, vacancy, property management, tenant damage, legal fees, etc., etc., etc.).

The seller’s failure to insure the underlying payment is made in a timely manner will affect his credit score, not that of the buyer.There are a several legal instruments used for wrapping an existing mortgage.

Expenses are things like taxes, insurance, utilites (if you pay or during vacancies), legal expenses, CPA, maintenance, property management, tenant damage, etc.Capital items are big expenses like roofs or furnaces.

If you want professional advice, you should always seek competent legal counsel from a broker or an attorney): 1- Do a cash-out REFI of the property BEFORE moving to give me some liquid cash. 2- Lease Option the property, but have the entire process run by my investor's club (they handle property managment, maintenance, tenant contracts and a TON of other stuff so I don't have to myself). 3- Use a portion of the liquid cash to purchase another property.

Everyone is always advised to seek legal counsel.

Here is a clause I have in my assignment contract:Assignee agrees to stand in the place of Assignor, and agrees to indemnify and hold harmless Assignor from and against any claim or action which may hereafter be brought or asserted by Seller against Assignor arising under or by virtue of the AgreementThat should be sufficient protection against any litigation that comes across your way.Although I would have an attorney look over any clauses in your assignment contract to make sure they are in line and legal and maybe ask to see if there is a clause you can add to further protect yourself.