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

That is likely cost-prohibitive.

In fact, New Jersey law prohibits you from listing personal identifiers on the form. 

Prohibited Transactions: Avoid transactions with "disqualified persons" (yourself, family, etc.).Alternatively, consider leveraging a HELOC (Home Equity Line of Credit) to access capital for investments.

. - If you come across the same tax expert on multiple threads, and you consistently like their responses, send them a PM via Bigger Pockets or contact them via the contact information listed at the bottom of their comments.IMPORTANT: we're prohibited from offering our services to you, both publicly and privately - unless YOU initiate the conversation from your end.Still, some people choose to ignore these Bigger Pockets rules and will send you an unsolicited PM or even post publicly something like "give me a call, happy to chat."

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.

Nothing in this Section prohibits either party from filing a lawsuit and recording a lis pendens affecting the Property, before or after the date of written notice requesting mediation.

And agents are legally prohibited to engage after closing - at least per Wisconsin State law. 

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

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."