I've decided to not attend college, so I can achieve financial independence faster and to avoid student debt.

Single-Family Homes (SFR) offer lower purchase prices, easier management, and better cash flow, while Small Multifamily (Duplex, Triplex, Fourplex) offer better cash flow, economies of scale, faster scaling, higher purchase price, complex financing, and tenant management.Good luck!

They're typically more expensive than a bank or conventional financing but can close much faster and tend to accept borrowers who can't achieve bank financing.

Remember, "the Bigger They Are, the Faster They Fall" in the next downturn. 

Having a plan to reduce the price or offer incentives can help get tenants in there faster, which is key to keeping your cash flow steady.Overall, you’re in a good spot with that ADU, and with a bit of flexibility in your strategy, you’ll have options that can really work for you in both the short and long term.

I guess I was trying to run faster than my brain.

We used to own all of our houses but are about 50/50 lease vs. own, mainly because leasing allows us to move faster when opening additional houses. 

It goes in much faster and is more water resistant. 

Thank you for the valuable information @Mike Lambert  Aside from banks, is there other institutions we could get the refinance faster here in Portugal? 

Faster is better but you don't typically need the fastest available.