I recently finished an awesome house hack and am hoping to finish strong with a HELOC to let me continue investing. 

For example, if you already have the land:what are the finishes you are planning to use.

We are upgrading all the counters to granite, painting cabinets, carpet to LVP, hardware from a basic brass to a matte black with copper finish, putting in ceiling fans etc.

Desperately seeking out any tips, tricks, or solutions those more experienced than us in this would recommend to prep the floor for tile in the most cost effective way; keeping in mind the rest of the house is finished, so we are trying to minimize damage to cabinets/drywall etc.

Get a few people that are handy and hire them for jobs but do request that they should finish on schedule and always always keep looking for better prices and quality some handyman start to increase prices over time.

It really depends on what kind of finishes you want and how many bed/bath each unit is.

I just finished writing a letter that I’m about to drop off since there a notice on the door to do not disturb.

You want someone who is communicative and helpful, who will walk you through the process start to finish. 

2) You don't have either of the above to go the owner/builder route either.So your only option is:3) Hire a GC to finish this for you.

The last thing you want is to think you are finished and the odor lingers.