Another way would be to get someone to prepay you today for a job you will do over the course of the week or something similar.
We just sold a few things around the house and made about $250.
I wish I had done this much earlier in my life. I would have had way less stuff. I unfortunately had a "learned helplessness" syndrome about selling old stuff.
The money is of course nice but the things you learn about selling is and negotiating is really cool.
And finally the peace of mind that comes with having less stuff is probably the best part.
I used to do it with facebook pages. I would check out local businesses (any city) that could go for a custom facebook page. I had some templates that I could customize really quickly and would throw up a mock page. If I could get through to the decision maker and show them the example, I was about 20% successful in a sale. Considering the costs were just my time, I was easily profiting $100+ a day by making 10-20 calls and emails a day.
I recommend you keep it simple and small though, at least at first. There is a website, fiverr.com that has people who list jobs they will do for $5. I have resold some of these jobs for well over $100.
I don't really want to give away my best methods on here and the best gigs, but msg me if you really need some help. I would recommended combining the sales process in my post above with the outsourcing method of this one.
Good luck.