I would think 5k or 10k would be plenty, though it will depend on house size, age of roof, windows, sewer, AC, Furnace, electrical, plumbing. 

When I asked for a quote in the past on potential properties I told them age of roof but didn't specify pitch.My primary has a portion that is flat die I the add on years ago.

I build new construction duplexs, althought at a much lower size then yours (1800-2450ft2).  

But one thing to note is with section 8 tenants, and chasing rent, many times their portion of the rent is small.

You might want to get some solid leads on who is willing to do the refinance portion of the BRRRR.

Residential property on a street with similar lot sizes. 

Depending on the size of the deal that wholesale fee may be nice enough to just cut and run and play in your own backyard like Steve said.

MartinMy dad started in the land business in the Santa cruz mountains  Loch Lomond area in 1964.. bay area folks were buying lots for weekend homes.. ton of land in those hills. and if your lucky enough to score a mid size acreage with redwood you could log it as well and make a bunch.

Depending on the size of the building we would propose 5% to 7% of the monthly rent. 

We are a decent sized wholesale group in a few markets in Florida.