I also suggest they supplement with window units. 

I wanted MLS access to be able to run accurate comps and supplement my property searches via marketing.I think your last statement may be the way to go.....I don't currently have any realtor friends but maybe I could work out an arrangement with one somehow - off the record.

Collecting supplemental passive income from rentals now is part-time while he is working;Wholesaling and fix-and-flipping is very time consuming, so I can see why it would make sense to want to start renting out properties before being able to devote the time it takes to be a full-time investor.Where it seems slightly "backwards" is that the money to buy the rentals can usually come from assigning contracts and the profits from flips...

it would actually be better for your brother to ditch his friend and start his own business and work part time at a different company to supplement income. being in the trades I can tell you first hand that 90% of the co-workers I've ever had have pipedreams of quiting their job and starting their own businesses, which is fine but they don't have enough work, already have huge debts, don't understand business expenses & when they do start a co they end up behind on their taxes etc.

The concept is similar for you I think, you can buy cashflow producing assets and it'll subsidize your lifestyle until one day you decide to move to a cheaper area to retire, then you will have the cashflow to supplement your retirement.Hope this helps. 

Anyway....Don’t take this post so serious, it’s only an observation over months and months of zero contribution supplemented with uniformed advice. 

Ultimately we'd like enough properties with enough cash flow that we can use that cash flow to supplement our income at 55. 

As for my goals, I'd like to supplement and eventually replace my 'day job' income with passive income from real estate. 

The ultimate goal is to build a sizable rental portfolio to supplement my income and achieve FI by 35. 

It is fine for a hobby landlord to supplement a tenants rent but not if you are operating as a business.