A lawyer should be retained based on personal recommendations. But having said that, a lawyer will charge close to or more than those 30 hours were worth, so it's not worth seeing a lawyer over it. You can take the owner to small claims court to try to get the money and you don't need a lawyer for that. If your boyfriend can find any documents that can support his story, that will go a long way towards convincing the judge to rule in his favor.
You might be able to
find a pro bono program in your location where you could talk to a lawyer for free.
If it were me, I'd suggest finding another job asap, because if this owner will screw him out of 30 hours, he will screw him out of more in the future. Life's too short to work for crooks.
Oh, and he shouldn't sign that contract.