When I purchased it the building was 2 1 bedroom units with a bonus odd room that was being used as a bedroom and 2 2 bedroom units.

I am a military recruiter, and one of my recruits that I told this to already had a ton of different credit cards as he would sign up for new ones all the time to collect the signup bonuses. 

Don't plan on any appreciation, that is just a bonus.

Something you brought up that I haven't seen anyone else talk about yet, is your bonus entitlement with VA.

But seeing as this land is just sort of an unexpected bonus to an already good deal, I don't really have a target for what I want to make on the deal, and quick and easy sounds great right now when I have lots of outstanding debts from the rehab of the house.Is there a good mathematical way to decide?

You can put a generous earnest payment, maybe $5K to demonstrate you are serious.For lending I would suggest you get an "All in ONe " loan.

Sounds like a flat fee with payments and possibly incentives (bonuses) per milestones would be a good fit for you.

An added bonus is no more lost rent checks or money orders.

Bonuses when i'm trying to brand my business and get my landlord name out there in a sense.

Reason for initial acquisition: in addition to our normal checklist (distressed, mismanaged, rents below market, renovation needs were high, walkable distance to new LRT, in one of our targeted areas/street etc), the added bonus feature was that our architect confirmed with 90% certainly at the time that the entire building's 1 bedrooms could be converted to 2 bedrooms, (of course) subject to permit results.