They're all over the Strip. Or was it New Vegas Redesigned 3? I didn't think super mutants could do prostitution, due to lack of genitals. Seems like it was a game oversight, either devs forgot to put generic prostitute characters or the engine for whatever far out reason wouldn't let them. On the console generation that New Vegas was released on, the engine had nasty performance and stability issues if a cell got too big or had too many actors in it. Aside from what you could think of as VIP specials the ones you recruit, I believe it's meant to be implied that regular working girls are there somewhere , just they didn't have the specials.
Felicity. Age: 32.
Just had a look at the wiki and it turns out that super mutant hookers are actually a thing.
Tiffany. Age: 30.
Sex Workers and Sex Slavery in 'Fallout: New Vegas'
More than 1 in 10 of your posts or comments being self-promotional is spamming. Freeside and the Strip had to be broken into smaller areas so that objects and NPCs could be packed densely enough that they didn't look like ghost towns. At least casinos wouldn't be ghost places, that's for sure.