Furthermore, I often find it's much easier to convince buyers to sign with me than sellers by telling them that classic line: "Oh, did I mention that my services to you are free?"

YES, open an LLC as it can absolutely make is easier to obtain mortgage financing on Rental / Investment properties...in many situations.  

It ended up costing us the carpet cleaning fee for the only carpet in the unit.

You're not wrong, assuming that there is a clean paper trail: the loan proceeds were used for nothing but business.

So it’s a little easier to model what “downside risk” looks like for me.

It costs the same to repair a refrigerator, change a lock, clean a carpet, whether the rent is $500/month or $1,500 per month. 4.)

If after you account for the work needed to be done the deal makes sense then great, if not, don’t be afraid to walk away or ask for seller concessions.The more often you go through the process, naturally the easier it gets.

On the RVs you’ll want to know how long those people have been there, do they pay annually or do they only stay for the 3-4mo “season”, if seasonal do they pay a premium versus the annual, are sites open for short term stays (daily/weekly), how are the surrounding RV parks occupancy...The longer the term the easier to manage, less of a business.

Seriously, it was worth the extra money just for much easier it made taking the test.Unfortunately, I took the test in Tampa (Tampa School of Real Estate), so I can't help you here with an Orlando school.

Easier said then done I know.