Myself? Being a newbie at this, if in your position - with having free access to larger machines at work, and being really limited on space at home - I'd be spending a lot more time at work, after hours. But, that's just me.
I spend enough time there. I'm also off in the summer and have no desire to drive 60 miles round trip. I'd have to take my kids with me, too. I'd like something I can use at home so I can create projects for my students and also use it for myself.
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I think your 50% rule has you bottom feeding in the extreme. Recommend you ditch that rule and find a clean, used machine at a fair price.
Like I said, it's not really a rule so much as a guide. I've seen decent machines sell in the $600-800 range. I've also decided that a bigger machine is not for me, so I may take another look at smaller (and cheaper) machines. I got time, I can keep looking. I keep learning more and more, so when one does come up, I'll know its a fair deal and I can jump on it.
Thanks for all the input, I really appreciate it! It makes me think.