Here's what I've observed: in the areas with the best growth potential (for both rents and appreciation), existing small multifamily is very scarce.

Big difference in time commitment, risk, and potential profits 

Both have their own unique advantages and can offer great potential for real estate investing.

Appreciation potential certainly may be there but are you ok with neutral or negative cash flow?

Factors like zoning regulations, property size, and potential impact on your primary residence need to be considered.The ADU process can take time.

Also I have the potential to buy the neighbors lot of another acre guessing I could get it for $300-400k.

Since then the company decided to overhaul (and temporarily close) their business and sold off the properties, and investors got a payout from the sale proceeds of the properties they invested.

Risk:Retirement communities often enforce age restrictions, thereby limiting the potential tenant pool. 

STR saturation is market specific so you could look for a market that has STR potential and do RA there.

You want to be protected from all losses and the rent check not coming for a year while the unit is being rebuilt is one of those potential losses.