Since you haven't specified what dollars you're charging in, I guess you're in the US. In that case yes, prostitution is illegal and it's a good idea to avoid incriminating yourself. Euphemisms are often used (such as Greek and French), but I don't know if they help or not.

Enforcement varies a great deal in different parts of the country, but even if I knew where you were I'm afraid it's not something I have any knowledge about. I also wouldn't know whether your rates are reasonable (although the numbers certainly are odd), even if I knew what state you're in and whether you live in a large city or not. Have a look here, you need people who know about local conditions to answer your questions.

$50 sex is available but no, those aren't escort rates. And yes, you're bound to get a lot of timewasters, especially guys who troll the ads looking for new advertisers. Asking about services isn't a sure sign of a timewaster, but a lot of men just want to talk about them without putting up the money for a booking.