Unfortunately that isn't alwaysthe case but here are a few of my past sellers that can vouch for how I do business and that I will perform as we have agreed if you decide to move forward with me."  

zipcodes to consider.....21239, 21213, 21206.....good and bad exist in each of those, one must know the neighborhoods, streets, and blocks to accurately determine good vs bad. 

If it's just a numbers question, and the numbers are accurate, buying at $46K, rehabbing at $25K, and selling at $105K works as long as there are no unforeseen additional costs outside of the ordinary.I'm skeptical based on the photos that that's a $25K job.

How do you think we've been able to obtain millions in loans on non-performing multi-family and both of us don't have a job?

There point if valid but not accurate due to no construction to the stair in this case. 

If you could perform the BRRR strategy, factoring in ALL EXPENSES.  

Research your tax rate to get an accurate idea!

Owner financing doesn't make this a deal, it just sets you up for foreclosure when you can't refi, based on the Real performance of the properties, 2-3 years down the line.

I am specifically looking at 3 and 4 unit buildings, and I don't know how to accurately estimate these costs.  

I have one right now here in Oregon we actually had to sue for performance we gave a huge deposit which the lady kept and spent and then she would not sign the deed I have had 6 figures sitting in escrow ready to close since last May..