How long does it usually take to hear back from a potential employer? Because I've sent out 20 applications in 3 days and I haven't gotten a single call back.

I only received 1 call on my voicemail from a recruiter from a hiring agency, I called them back first thing the next morning and left a message telling them yes I am still very interested in that position, but that was 2 days ago and I haven't heard back from them, so that's a little confusing.

I have held only 3 positions in my life - I'm 22. Been working since my senior year of high school where I was a volunteer teacher's aide for six months, my next job was at a retail store for only a few weeks but I hated it and quit and obviously didn't write this on my resume, my next gig was another volunteer position at my mom's university where she works, I was a volunteer office assistant for a couple years part time.
Then I got my current job that I've been working at since 2013, it's a part time at home job as a marketer and customer service consultant where I make a commission not an actual salary. So on my resume I just have 2 part time volunteer jobs, and this current job as a part time independent contractor. Is this why I'm not getting any call backs?

Also, I am astonished to see some jobs out there saying "$10 an hour, must have a bachelor's degree." Wow, if I had a bachelor's degree I would never take ten an hour. But I don't even have a degree. Competition out there is fierce.

I've been applying to mostly receptionist and data-entry positions in offices and hospitals. Not even an interview offer.