Normally, Single garage is pretty safe,but it is NOT legal at all. Police will only take action if the neighbour complians. When ppl complains about the place and If the cop can proof that the garage invloves some Illegal activities REGULARLY, then the police will take action. MOREOVER, if u are caught in the garage when the cop is there, then u will be trouble. BUT of course, it takes a lot of investigation in order to get enough evidence to prove the place is a ILLEGAL ( i forget the TERM for the garage..somebody?).
So, in conclusion, single garage is safer cos' it catches LESS attention from neighbour cos' of LESS traffic....BUT again, it is not 100% safe....other inputs??