I am now considering renting by the room for my current house.

The consider the materials used, etc, but they do use area comps of newly constructed homes as the value.

Perhaps consider the modular route instead.

Hi, I set up a Solo 401k last year to start funding my investments in real estate.

It costs so much to sell a property and buy another one, and is such a hassle, that if I were in this situation I'd strongly consider just paying the special assessment and keeping a property that's otherwise great.

Looking for some feedback on an idea I’ve been considering.  

Should I consider taking equity out of the house to invest in more real estate, or are there lenders who can work with my situation?

Set clear, simple goals and break your 10-year goal into smaller, doable steps.

Quote from @Hieu Le: Most HOAs consider a short-term rental to be a business, not a residence.

You may want to consider working with your accountant remotely to expand your options.I would also recommend looking for a tax strategist willing to work with you throughout the year, not just when preparing your tax return.You want an accountant who can help you strategize and who is responsive when you want to know the tax consequences of the financial decisions you are making throughout the year.Good luck.