@Eden Meng contact your Solo 401k administrator regarding regulations regarding leasing  mid term and long term rental properties.They should provide guidance regarding prohibited transactions.

Byzantine planning and landlording regulations.

Consider exploring financing options like FHA loans or conventional loans with low down payments, understanding local regulations, and conducting market research to ensure you can cover your costs.

Trump did not address housing as directly but has previously suggested cutting regulations and using federal land for new construction.Sharing this because it could have a significant impact on the housing market in the near and long term. 

@Jeremy D.2nd kitchen and you would need an ADU license, and of course needs to meet the adu requirements.An adu is not multifamily, so yeah cant have the 2 parts rented seperatly when you leave.Whats unclear as I dont think its adressed in the regulations, is if you have an ADU, would 5 persons be the total property limit.

My understanding is the TN has some crazy rules and regulations that complicate this process.

Here are 2 articles talking about new regulations they're trying to put on STRs there, which definitely could impact your rental income, especially if you buy in an R-1 area. 

Compliance issues regarding local landlord regulations not an issue in my area.

Colorado is quickly becoming on par or maybe even worse than California as far as landlord/tenant regulations. 

In making this determination, the enforcement agency shall consult with the entity responsible for enforcement of building standards and other regulations of the State Fire Marshal pursuant to Section 13146.(4) The enforcement agency shall not approve any applications pursuant to this section on or after January 1, 2030.