I have recently started diving into the idea of house hacking to start my career in real estate so bear with me...I have no actually plan yet as I'm still learning but I'm gonna run down an idea I have in hopes to gain some knowledge. 

Hey my Name is Nicholas, I'm running into a problem with financing, little bit of a backstory I've recently turned 19 and have been working in solar sales for the past year and before that I was working at a pizza place.

Reading between the lines, if they were open to a concept shift, they weren't open to it soon enough to make the pivot before running out of money.So my buyer picks it up for a tad under what the seller paid for it, a few years ago, before the $500k in upgrades.

Many of your recreational campgrounds are owned by the government (either state or local) and almost all of them do not allow you to stay more than 21 days so if you are running a long term park there is a very high demand in many states. 

Firstly, I have 5 doors, 3 units total.

If you are using a conventional loan on the second home purchase they will consider the mortgage on the FHA loan, so you will run into issues qualifying with your DTI, unless you have enough income to support both mortgages.

However, if you haven't already done so,  I would talk to a real estate agent in your area that specializes in flips, and get them to run comps for the current house vs. the added square footage.

Hi John, I’m based in Seattle but invest in Memphis and Detroit where I now own 9 doors.

You most likely will not find a property that cashflows like that, but in the long run it still could be a very good investment.

They "party" (slamming doors, talking ludly, and throwing up in the bathroom) until 5 am.