If you ONLY have L1 equipment, you could post-process to the local NGS_CORS, if you are in an area of relatively dense CORS coverage. I would hesitate to process L1 only to CORS in excess of about 15-20 kilometers though, and things can get tricky much past 10 km too. There is L1-ONLY post processing software available for free download out there.
Good (but old) L1/L2 systems (receiver & antenna) turn up on ebay all the time, and often can be had for $1000 (or less). I assembled a really nice system (antenna, receiver, cables, controller) for well under $1k last year (3 separate purchases), BUT I already had the requisite software (controller & binary-RINEX converter) to utilize it. Most (but maybe not all) manufacturers have free “to-RINEX” converters available for their equipment, but I would verify availability (and connectivity) before buying anything.