Building up vintage bikes can be less than buying new.
Many don't want vintage.
A few of us don't need new to satisfy our biking needs.
I have at least 4 vintage bikes that cost me less than $400. These are quality bikes with Reynolds531 frames, vintage tubular wheels, etc.
It takes patience at times to find the right deals, but Winter is a good time for deals and you already have 2 to ride. CraigsList and Facebook markets are your friends.
YouTube videos will give you the skills, no problem. But a couple of steps need special tools.
Do you have access to a bike co-op? Friends with tools?
Nothing more satisfying than doing it yourself.
Learning new skills open huge possibilities for cost savings in the future.
edit: as post below states = my comments are for road and city, not mtb. Also, vintage geared steel bike will not be lightest by a few pounds, hence the reason for tubular wheels and nice tires. With integrated levers for shifting/braking, dual pivot calipers, and the gearing for your territory = you give up nothing to an 18lb modern bike, excepting mountain riding or sustained hill climbs and even then not really much (unless you are racing and care about seconds
Old cycling Truisms:
Train heavy, race light.
Better to have a moderate frame with great wheels, than a great frame with moderate wheels.
90+% of your race wins* are due to teamwork, cunning and personal engine output+endurance, not the bike.
*excepting time trialing, of course = engine output and aero position (The Bike) for non-technical, flat-out speed conditions.
*also excepting track riding, ya gotta have the right bike.
10 pounds dropped off the rider makes a faster racer than 4-5lbs off the bike.
Learn to support yourself on the road.
re-edit: this thread needs more pics.
Below a retro frame and fork, with 9 speed triple. My 'take me anywhere' road bike. It likes to head to the mountains of western WA.
Shown in final build stage. I wanted all Campy so not $400, but not much more.
I love the orangesicle color (Dutch frame) and chrome socks.
Frame is not Reynolds or Columbus, but much undervalued Ishiwata022. Purchased from BikeForum Classic & Vintage Sales = $100, never crashed, no dents and pretty good paint/decals.