With regards to age, I'd say you're only too young if you don't know how to guard yourself against people trying to take the piss, and if you don't realise that by putting up an escorting profile anywhere, you're inviting anyone who fancies trying to take the piss to do so. And that a woman can and should always say No if she feels like it (or doesn't feel like it).
So my main advice is not to bother giving anyone the benefit of the doubt. 100% of my good clients have been able to follow simple instructions and act like a sensible human being on the phone, via email AND in person. It's not hard so you will still get lots and lots of lovely clients even if you're very strict. I know it's hard to stick to your guns when you've got Mr I'm Your Senior, Young Lady telling you that you're being silly or Mr Nutcase trying to confuse/scam you, but do not ever deviate from The Rules. The only times I've thought "fuck, I hate this job" are times that I've been too lenient and allowed myself to get messed around by a timewaster or, in a couple of cases, had my physical safety/health compromised by not listening to my instincts and stupidly meeting a weirdo.
The rest of the time, I think "woohoo, this is the best job ever". YMMV. You'll find lengthy diatribes written by moi on the issues of agency vs independent and by others (more useful) on taxes and relationships upon a quick search of the forum/recent posts.