It is a simple math exercise. 

The IRS has a 120 day redemption period, which they almost never ever exercise, and then their lien is void on the property.

. - Do you know how often lenders typically exercise the right to lower the limit?

I would collect a non-refundable option deposit from them up front, create a cash flow every month and if the tenant/buyer exercised their option down the road got paid again. 

(Like all liquidation options, they do have the ability to throw up a gate if too many people exercise it at once ).

The purchase price goes up 10% each year they do not exercise their option for a max of 5 years. 

Regular exercise and training are necessary.

The seller has offered to finance at 7.5%I contacted to seller to ask questions and get a feel for his need to sell but he is only dealing with me via Email, and I still only know the cross streets.I asked him in my last email about the Lot size, the Address, if the are any back taxes, if he is the owner or someone selling for the owner.....Questions:If I am able to talk with this gentle man on the phone, what do I ask him?

Gently serve copies of said time stamped legal documents to your "tenant" and respectfully ask for the arrears.

Tenants will not usually be as gentle as an owner.