I think I know the building and there is not much to consider with this type of use: if chemicals were used your lender might require a phase one envirmonmentals study, but I don't think that's the case here.Issue number 2 is that it can take a while to find a new commercial tenant, so while tenants typically stay a very long time, if you have a turn over you may have to spend some money on preparing the space for a different use and it could be some time before you have a new business.

Did you take a look at the link I included above to the harsh truths of google reviews? 

What about the main stack and the vents that feed the main stack inside the walls (I have seen a nightmare of holes in these one time from backups and probably harsh drain cleaners over the years).

@Jonathan GreeneDespite your harsh comment, I have gotten my name out there.

You mean harsh! 

Inferior might be too harsh for some, another term is they are the insubordinate in the relationship. 

The plumber quoted $900 to jet it out, or $3500 to dig up and replace the pipe.I see there are chemical root treatment options for this that is much cheaper.  

However, I've been in harsh winters before and maybe I'll travel that time of year, or who knows, right?

Chemical treatments can mask smells, for awhile.Fire restoration is a specialty and I'll bet the inspectors will be very tough on a new guy breaking into the business.

For example, Del Mar passed a regulation that banned STRs in residential areas, but the Coastal Commission ruled the ban was too harsh and indicated Del Mar could not make such a stringent ban.