I found an off-market duplex with ADU that is non-conforming, and I would love to buy it to rehab it (keeping all 3 units).

Then 4) I would get laser focused on 1 or 2 good markets with a realtor that is also experienced with flipping and can help you find good deals. 

Reach out to a few and see who you like.You can also ask members of your local real estate investors association for real estate accountant recommendations.Good luck.

Homes are staying on the market a bit longer, and we’re starting to see some price reductions.

I also have marketing skill and tech skills.

When I purchase portfolios, I typically have it funded by a small local credit union or bank, e.g. a portfolio lender.

This will help you identify what market will have the most ideal factors for what you're trying to achieve with real estate. 

Compliance issues regarding local landlord regulationsE.

MFH carries all of the emotional issues and local governance that tends to favor tenants over landlords because you're dealing with "people's homes", not an investment property.

If not, you can't buy in an LLC unless you are paying cash or using a local bank who knows you and is willing to use your account as collateral for a new LLC without two years of tax returns.