In a 1031, from the gross price you would subtract the costs of the sale such as real estate commisison and transfer tax and other seller expenses. 

I have refunded them pro rated based subtracting the one week it was taken off the market in the lost opportunity to rent.

You would then subtract your current mortgage from that 80%.  

That amount got subtracted out from his K-1 passive activity income of $300,000 leaving him with $148,000 of taxable passive income.In 2018, the top Federal tax bracket fell to 37%.

Multiply the Arv by .7 and subtract the rehab That’s what you need to be all in, simple 

This depends on a few things - for passive real estate investing if you want to take deductions from your personal W2 it's going to depend on 1) REP (real estate professional status) - ie: need to work 750 hours plus on RE and work 51% of your work time on RE AND 2) Your income (they subtract the amount you're allowed to deduct based on your W2 income - they subtract 1$ of your deduction allowance for every $2 you make over 100k at your W2 job...so once you get to 150K you can't deduct anything from your personal W2 job, you can only pass it on to later years, deduct when you sell etc (the maximum allowable deduction is 25k).

And then I would subtract 1/2 the remaining life span.

This comes to 341,250, and as an investor I would look to be all in for 75% of ARV, then subtract the cost of repairs to get the unit's rentable at 650.

A co-worker of mine recently mentioned to me there is a re-keying fee ($80) upon move-out that will be subtracted from the security deposit for the apartment she is thinking to move into.

It shouldn't be counted as a debt, but will see if you have enough funds to pay that off within 3-6 months and will probably subtract out that amount from your available assets.