All of the businesses you own come into play when your Solo 401k eligibility is being determined.

How do you evaluate potential investments, and what role does financing play in your decision-making process?

The main play with turnkey rentals is appreciation and paying your loan down over time. 

It seems you have a great income already and a cash flowing property in Pennsylvania, so are you comfortable with something that breaks even and is an appreciation play or are you looking at purely cash flow?

Wherever you do invest, try and play by the rules.It can be a very expensive learning lesson which it looks like this will be. 

I know this is very ambitious, but I have always had big dreams (like playing D-1 baseball in the SEC).

LTRs are usually a 'safer' play, particularly if this is your first real estate investment property.

General appreciationIf it is in a solid area, maybe the play is appreciation and then a few years later do a 1031 exchange to another, better performing property.With multifamily, typically you can't do STR, but maybe MTR?

I would assume little to no appreciation over next five years so I would model it and see where it plays out

Generally speaking, they will not play by your rules, take kindly to rent increases, and will be difficult.