I think the advice of billing them early but giving them time to get the extra money together is a good way to proceed.

If 5+ acres then what is your plan for all that extra land, and do you have the money on hand and the local regulatory environment mapped out to execute that plan?

Making extra cash on the side is always fun.

It's more conservative and while my rate may be higher and I will pay a little extra in interest over time I can still accelerate my payoff.

It will potentially give you some extra freedom.  

One extra measure of protection I very often take is, depending on how bad their credit score is, I take extra deposit (an extra half a month, sometimes whole).

Anyone have suggestions, or know of flippers in the area that could use some extra help?

Look at 3br/1ba houses vs 3br/2ba houses and quantify the difference the extra bath makes in price.  

I am working on trying to put together a deal on a multi family building and wanted to get some feedback on how much extra I can pay for a property in exchange for receiving seller financing.

i buy my properties in rochester ny now with buying the new 4 extra property i should be  making 6000 a month but will own 50,000 in credit card now that i use credit for buying 4 houses cash