nothing.
$1K rotovap https://sfbay.craigslist.org/nby/for/7551260374.html (try lowballing them)
& $45 -$100 worth of kegs https://sfbay.craigslist.org/eby/for/7542537211.html
see: Optimizing your RotoVap for how/why
to run it you’ll need cold. one solution would be reconfiguring a AC unit. https://sfbay.craigslist.org/nby/app/7545686313.html 2500k BTU for $75 is pretty hard to beat.
see: Chiller Hack (DIY) & Suggestions for diy glycol chiller fluid? amongst others.
although I’d budget at least another $2k for expert guidance.