I used to think that would prevent me from having success.  

If so,maybe your brother is trying to prevent your siblings from being offended that you only will profit from the sale by way of a 2 or 3 percent sales commission,have you considered that point?

Dealer classification also prevents you from using 1031 to avoid capital gains taxes.

In short - get your license.... it's worth it to prevent the pain and hassle of defending yourself in an investigation.At times this business is awesome, and other times it's not incredibly fun - so no matter what niche you pick, you always have to figure out how to mitigate as much risk as you can... and the sandwich scenario you mentioned is fraught with more risk than walking into a room full of angry hornets naked.

Well, if a client of mine sent me a message regarding that type of problem there would be several factors to consider:1) replacing the broken pipes a) what type of pipes am I replacing2) are all of the ceiling joists in good shape3) what areas need to be dried to prevent mold?

Also looking at what preventive maintenance can be done to help reduce future large maintenance expenses.In regards to building relationships, I have a post coming out soon titled Successful REI Takes A Team: Our Roster.

He has not put up a "For Lease" sign outside the building or advertised the space on his firm's website (possibly to prevent offers from other brokers). 

No way to know EVERYTHING when you close on your first deal, but if you know enough then you can hopefully prevent major pitfalls.2.

An insurance policy does not prevent you from being sued and losing your assets.

I want to prevent the buyer (who is an agent) from moving forward on the deal without me.