Don't offer it on any profiles, but if you get a client when it feels right suggest it to him or if a trusted regular asks you can choose to agree.
I can be sub in 'real life' but found it a whole different kettle of fish doing it professionally. I then found that 'proper' doms who are intelligent and respectful sometimes picked up on my subby side and I will go a bit further with them if it feels right.
Not advertising it won't stop the idiots who think surprise slaps to the arse are nice, but then we all deal with them!