You're probably going to get a lot of "don't do it, this isn't the right way" comments, and that's fair (there's some validity to it), but you've got your reasons. We all have different journeys. Personally, I lost my virginity the same way---and at about the same age---but to a streetwalker, rather than an SP. No matter who you end up with, you'll have a better experience than I had.

(Editor's Note: Insert "and I turned out fine" comment here.)
I agree with booking longer than 30mins, though. You don't have to turn this into a whole thing if you don't want to, but it's still more than just running out for a burger. If you can wait and save up a bit more it'll be a better experience. (Especially true if you're not interested in Asian agencies. They're sometimes cheaper.)
You'll also want to look for the term "GFE" or "Girlfriend Experience." (I don't hobby in Southern Ontario very often so I don't have recommendations.) The difference is difficult to describe, but it's there; be with a girl who'll make you feel like she enjoyed the experience as much as you did.
One final piece of advice (unless this turns into a flamewar and I come back for more lol): I'd avoid telling her it's your first time. Some girls will be fine with it, some will be honoured to be your first, and some will be freaked out. You won't know how she's going to react in advance, so personally, I wouldn't burden her with the information. They get lots of inexperienced guys so you don't have to pretend like you know everything; feel free to tell her you don't have much experience and leave it at that.
If you get a bunch of SPs coming out of the woodwork with offers, you can disregard everything I said.