To add to some of those that you have already mentioned.Red: No written contract and wants money up front (assuming you have not est a relationship).Run:  Absolute piece of s*** vehicle that usually does not fit the stereotype of the trade they claim to be a part of.Red: Cant return a phone call in a timely fashion.  

My entire professional background has been spent working in construction, through several trades and companies, with my favorite skill set being finish carpentry.

The fact the you are asking this question for your friend is exactly why so many blue collar trade owners go out of business or struggle for ever.

Investors trading flip houses back and forth etc.

Short term stock trading/option trading is a completely different animal.  

Hey there BP, what cap rates are 50 units and down, value add properties trading for in he Atlanta GA markets?

In my experience, local homebuyer assistance is usually a trade-off; money for downpayment or closing costs in exchange for a higher interest rate.  

@Ben W.You will not find assembled-for-you lists of most of the information you list above in Canada as privacy law makes trading in such information illegal. 

I would lean toward one of the building trades.

If your family can swing it buy a four plex.