ultra wide angle

I think my wife just got sold on my idea to buy a used ultra wide angle and reselling it after the summer.
We have a trip to Vancouver in a month, followed by LA/southern california a month later.
I expect to lose about $50-75 on the transaction between a retailer like keh.com and reselling (to them or to Ebay), which is about the same as a lens rental for the week (which would include two travel days) for Vancouver alone.

The hard part will be selling it after the summer. But, if I had $500, I don't know if I'd be investing in that specifically. Though I'm torn on whether a long term purchase for similar money would be an ultra-wide, or something sharp like a 17-50/2.8 Tamron.