Hmm, I could be very wrong but aren't there ways to emulate pcs? Although you would need one stronger in order to do so, I heard before that you could create a computer within your computer for testing purposes so long as you meet the requirements. Alternatively another option is using a program like Teamviewer or so to take over another pc of someone you know so you can test! That's renting, in a way, but hopefully free!
I totally understand not wanting to buy one for that, they are way too expensive and if you sold it you most definitely wouldn't get your money's worth. But either way, can't wait for the new content updates! I am sure they will be worth it. I can't promise I will be patient, but I will wait nonetheless! xD