That is in addition to clauses that require anyone that stays more than 7 nights in 12-months to apply (then it becomes our choice if they are treated as a temporary occupant or tenant) and prohibition of subleasing.

I looked at putting in meters direct to every home, but they would cost roughly $2,000 per meter if put as direct to tenant, which seems cost prohibitive.

Here is a video that runs down the basics - https://s-media.nyc.gov/agencies/specialenforcement/01-Legal...There is also a prohibited building list - https://www.nyc.gov/site/specialenforcement/registration-law...Here are some more info overall - https://www.nyc.gov/site/specialenforcement/registration-law..All of this makes STRs in the city pretty tough but it certainly not impossible.

Moving forward in my  commercial leases I will now include language making the placement of thermostats the landlords decision with additional language prohibiting the relocation. 

There are so many IRS restrictions and prohibited transactions within a Solo 401K that it makes it difficult to navigate.

I do not recommend someone who has never owned real estate to do a fix and flip as real estate is challenging and cost prohibitive, I recommend if never owning real estate to start with an asset that does not need major repairs. 

This demographic is projected to keep increasing over time, so I would do whatever you can to hold onto this property (ie cash flow well).Furnishing 700 sqft with PB or West Elm (you and my wife would get along great, Bonnie) won't be price-prohibitive and well worth the cost.

A "lake house" might be in a residential zoned area where a commercial use would be prohibited or at least require a variance (approval) to make an exception.

Or a personal loan if interest rates aren't cost prohibitive?

I generally see literature as such, and cannot tell if having a part time employee removes the chance of solo 401k or if the custodians just don't want to deal with it:"IRS rules prohibit contributions to a solo 401(k) if you have full-time employees, but you can use the plan to cover yourself and your spouse into retirement."