(I know new "help me make money quickly!" forum topics pop up all of the time, I don't mean this one so generally though

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To make it short, I'm kind of in a jam with rent and bills, and need to make $600 minimum, preferably $700 (would prefer not to temporarily live solely on oats, tuna, and water if possible) by the beginning of June.
I'm out of work until the middle of next week, I'm going back to personal training at a gym I worked for previously but can't get on the roster til then, and if all goes well I should be able to make the money doing that with time to spare, but since I get paid by appointment only I'm not hedging all of my bets on it. 1 week doesn't really leave any time for "temp jobs" or anything of that sort either, so that isn't looking like an option.
I'd be back earlier (probably now) if I weren't stuck at home with an annoying neck injury that's finally starting to improve, but unfortunately labor-intensive random gigs like moving probably aren't the smartest thing to do and risk screwing my neck right back up (I haven't been able to lift weights for nearly 2 weeks, just light cardio, and am about to go insane!).
I don't really have a lot of stuff to sell, just sold a big bunch of things on Ebay and did alright, but the $600 minimum is my goal AFTER those sales. I'm going to dig around some more for random junk that might fetch $1 or more, but again don't see much panning out there.
I've been personal training on my own and doing alright for the last several months, but am happy to go back to the gym because of the wildly fluctuating nature of freelancing- having just a few steady clients of mine randomly flake out and disappear has taken a HUGE chunk out of my finances- I just don't enjoy dealing with this anymore.
I also currently have no major techinal/computer skills beyond the basics- I'm working right now on learning to build a web page, but as it is, those nice looking craigslist gigs of "Build my webpage, will pay $500!" just aren't a route to go either.
I'm about to start getting rid of a few things I'd really rather not sell, but don't really need either -I have an extra, older computer that might fetch $100. It makes a nice back up if ever needed so I like hanging on to it, but that's probably going to be the next thing going to the craigslist/ebay route.
Basically I just need some ideas for a short term "Oh ****!" moment solution of coming up with $600- it can be a one shot deal, as I have no intention of landing myself in this situation again! As always any help would be appreciated!