I'm not affiliated with these guys, was just basing it off their 'about' page that they are for college students.

I'm a cofounder, my name is Julian. I definitely understand your point and it has been a topic of debate with us for quite some time. However, we think that college campuses are perfect for something like this because of the pre-existing communities, and the security (albeit mild) that they provide. There are obviously a lot of students scrounging for cash, but we think that with professors (anyone with a .edu email) there will be a good amount of people posting as well. Beagle is also ideal for quick and easy tasks, so they probably won't be very expensive.