I'm just wondering if this is within the site/forum rules, and if so, what the correct place would be to do so?

if you want to see the rules, either look at the teeny tiny eensy weenie nearly microscopic link that's at the bottom of every page, or go to Help.

I know you are allowed to sell services. Dunno if TPTB would consider that a service though. If there's ever a question about the Rules, remember you only get one account here and it's in your interest to protect it. File a Ticket in Help and ask. That way you can be sure.