Bonus points if I can incorporate technology to streamline applications.

That one will take a year, but then it will get 25K a month on 2.5M, and there is an RV park as a bonus.   

More work, more time but you can take advantage of a nice cost segregation / bonus depreciationThis is the truth! 

Remember, investing 200,000 into an ADU won't likely increase your properties value by 200,000, but the rent potential is a great bonus.

If you go with the partnership route1) You need to manage the money going in and out of the business bank account.2) File a partnership return and be responsible for issuing K-1's3) make distributions to you and your partner for cash flow that you receiveYou will likely spend many hours on a nice gesture.I may want to consider instead to give a christmas gift or a bonus for early completion of projects.

Bonus if you have any advise or pools. 

Bonus rule:  this applies to any investment or business that even HINTS at being a scam, below board, or ethically questionable - If you don’t know who the “sucker” is, it’s YOU. 

@Cate DeBates Triple Net commercial lease is a huge bonus!

But it also means you have virtually zero bargaining power as the seller can reuse any and all repairs and just keep your 6 months of rent as a bonus. 

Non-passive to achieve this level of return.Add the addition of the ADU makes the main unit rent controlled if over 15 years old.the work to add an ADU likely exceeds the effort of a brrrr that can achieve infinite return  Experienced investors are adding multiple ADUs by leveraging items like bonus density, committing units to affordable housing, etc.