Depends mate.
It's only my worth what someone is willing to pay for it.
How long does it take to get round, wfp or trad, cash or online etc etc, so many factors
Personally I would start at 10x and reduce it until someone buys it, but depends how desperate you are to sell and the quality
400 customers for 38k seems a bit on the low side price per property but again it depends where abouts you are.