There are many people who, when actually own a boat think that they have bought a pile of scrap. This is not the case in many instances. Go with Chris Pink's suggestion which seems sensible. Talk to local boaters rather than the marinas/boat yards to find local liveaboard welders. In my experiance they are more friendly, professional and cost effective than my local marina.
He might be able to cut costs by doing a barter or skills exchange or working as a gofor. There will likely to be some prep work that he could do himself rather than pay someone to do it. Boat yards are more likely to make the job more expensive than it needs to be.
Lets see some pictures of what he has got.
Tim