>>1497277I understand your sentiment, feel this way about old bikes, too. I love the thin tubes, the lugs, the non-sloping top tubes, fancy colors, crome parts, rim brakes you find on 80s and early 90s bikes.
On the other hand, there's a lot of (semi-)modern tech I wouldn't want to miss out on. Cassette hubs, dual pivot brakes, indexed shifting, STI brifters, alloy rims, low-friction cables, grippy but fast and resilient tires, ergo bars...
Maybe some general remarks:
1. Always buy the most modern bike you still like from an aesthetic point of view. Chances are you'll have less issues with compatability (e.g., recessed brake mounting, hub spacing etc.) and will be able to carry over at least some of the parts.
2. Builds starting with a bare frame tend to be the most expensive. If the bike comes with a functional headset, stem, seatpost and bars, that's already a lot of money saved. Also, even if you end up changing all of the parts for their more modern counterparts, you'll still be able to sell the old parts on the used market. Sometimes, that's even close to cost neutral. I recently sold Shimano 600 brakes and crankset for exactly the amount of money I previously spent on Ultegra 6500 brakes and crankset. Both used, obviously.
3. Be prepared to spend money on tools you'll possibly only ever use once or find a good bike shop. For example, to make a 130mm hub really fit into a 126mm frame without alignment issues that will results in shifting problems, you need to cold set the rear triangle, get the dropouts alligned and check the derailleur hanger alignment.
4. Buying a 10-year old bike in good working condition will be significantly cheaper than buying a 30-year old bike and upgrading it to ride as well as a 10-year old bike.
5. A good frame is of uttermost importance. No rust, no cracks, no dings...
>Pic related: 1991 Koga Miyata Exerciser with complete 9-speed Ultegra 6500 (early 00s), Rigida DP 18 wheels, Micheling Pro4 Endurance tires, ergo bars and so on. 