To get a roof put on, I went to the local church mens group and hired them for $500 + a case of iced beer (it was a Catholic church).
One day, 5 guys having a fun day of it, church getting a nice donation, and my house was done.
If you formalized that model via church youth groups or the local Food Bank (extend it to include a Job Bank) you'd have the local illegal problem solved overnight.
p.s.
Roofing isn't fun, even under the best of circumstances. It's one of the two or three worst jobs I've ever done. I HATE TAR!