If you find one of these neon signs be sure it is in good working condition before purchasing. Years ago I bought a couple at a yard sale for $20 thinking I had hit a treasure trove. Unfortunately, one of the signs did not work at all when plugged in and the other only partially worked.
Neon signs are made by using luminous tube lights filled with special gas. They were extremely popular in business windows from the 1920's to the 1960's. Neon signs are extremely fragile, always take extra careful measures when transporting or storing. The glass tubes break so easily and then your sign is pretty much worthless.
There are neon restoration business's, however, you can always tell when one has been restored as they do not shine the same. If a partial repair has been made on a vintage neon sign it stands out and screams I've been repaired. Not all Neon signs are vintage, do a little research before spending a lot of money.
Keep your eyes open at garage sales, yard sales, auctions and estate sales for these rare signs some are very valuable, some are highly collectible, all are pretty cool!