Gas leak in tenants unit

[Robinson Rice]

I have a duplex in Stockton CA and just rented to a young lady who complained of the smell of gas.  My husband went to check all the pipes and tightened all the valves and found that one was loose. The tenant came back and said that she still smelled gas and asked if she could have PGE come out, and we agreed.  A week later she calls and said that the smell of gas was even more prominent and PGE came out and found that there were 2 items leaking and fixed them.  When he went to check the pressure to make sure that there was no more leaks, he found that it was still showing something was leaking but and asked if there were any additional furnaces.  My husband stated there was under the house but it had all been capped off.  PGE guy informed my husband that there could be a leak from the furnace pipes under the house and that he would have to turn the gas off until it could be located and fix, which at that time, they could come back out and turn it back on after they check to confirm that it is no longer leaking.  

My husband is trying to figure out the worse case scenario.  If we have to go under the house and replace this and the price is more than we can afford and it is landlord condemned, meaning, we can't afford to do the repairs timely therefore, can we ask the tenant to move? what do we have to do for the tenant?  how can we avoid a lawsuit since the PGE man encouraged her to go to the doctors and that all the problems he fixed were fines (oh by the way, the items he fixed, were approved by the city as we had to get permits to install the things he found problems with).

HELP! THIS IS OUR FIRST RODEO!

Cheron Rice