Feel free to take or leave my advice, but I think others will agree that, for now, you should focus on maximizing your savings rate, building your credit, paying off any owed debt, and house hack your first deal—just my two cents.

Where people are still normal and you can evict tenants but generally you don't have to because people pay their bills here.  

Now, you need to figure out how to find deals and pay for them.

But since I'm dumb when it comes to such I may forever pay the price.  

We had success in summerlin with insurance company paying .. over a 24 month period we had 3 tenants   fair market rent at the time was about 2200 or so non furnished.. we got 4100.00I did not like the turnover so I put it up as furnished rental and got 3500 and its going into its second year with a superb tenant. so seems like a happy medium for us.. 

If your brother is looking to invest in real estate largely from a tax reduction standpoint they should pay a qualified real estate tax strategist to review their specific situation and what may or may not work for them. 

I do not understand your remark as related to the DSCR loan.  2 ADUs are not allowed by f/f conventional financing but is not always enforced.Fortunately if you stay with the current tenant without a refi, by the time you pay principle it is likely the rent will have increased enough to absorb the increase mortgage payment. 

Your son is likely paying more than the property is worth, by definition, as the seller would almost certainly prefer a similar offer that was not subject to. 

Now, you need to figure out how to find deals and pay for them.

So that with paying my investor 6.3%, they will get a passive income of $2,532 every month ($30,384 every year).