We had to replace our refrigerator in our rental, due to the old one breaking.

Our choice was to repaint and put in new carpet to replace the new carpet they damaged. 

I currently work as an embedded software engineer.

While you are correct that you’ll be relying on your purchase of the replacement property to go through, there are a few strategies to use and language to add to the PSA to try and keep a seller honest and protect you as buyer.The attorney negotiating the sale and purchase should hedge the risk snd build in flexibility on both ends.

Would you replace a current functioning 1000 gal septic tank to a 1250 gal tank in order to list my flip as a 4 bedroom as opposed to a 3 bedroom.

Some things I do to avoid bad situations: screen well, only have properties in good locations where people actually want to live (I find tenants behave better when they know they have a good thing going for them and that they are easily replaceable), set proper expectations, have a rock solid lease, go over it with new tenants to make sure everything is clear and agreed upon, and enforce the lease by issuing a formal notice to pay or quit every single time rent is late by even one day (and charge the late fee), or a formal notice to cure or quit every time there is a lease violation.

We have replaced about 2k furnaces over the years out there, about $1800 all done , remove and replace.

I have goals of obtaining enough MF property to replace my current career by the age of 50 (I'm actually shooting for $6K/m by November of 2026 because, why not?)

Does maintenance factor in replacement costs of the HVAC, Roof, Glass windows, structural piping, Parking lot repaving, sprinkler systems, etc. 

I heard that a friend had to give up a replacement because the relinquished property was not closed.