Got all of my faucets used off of e-bay 12 415 perlicks and 2 stout style faucets 1 Taprite and the other a Caffreys Irish Ale over time total cost $108.34 with shipping if you watch you can find deals works best when your not in a hurry but have the money ready to buy when you do find the deals
I just saw this now. Not sure what the Perlick 415 is but I spent $121.96 on 4 Perlick 525 SS ($30.49 a pop). You're saying you got 12 perlicks and and two stout faucets for $108? Even if that was just for the Perlicks thats $9 per faucet. Someone must have lad a lapse in sanity to sell them that low.
If I buy a set up for a single tap system is it easily convertible to a double? Or should I just buy all the stuff for double upfront?
It depends. If you do a mini fridge conversion than you are gonna be limited on the configuration of the tower. If you do a collared keezer, then the sky's the limit as you can always drill more holes. The same can kinda be said for coffin builds, but it depends on how wide you make the coffin box. But I guess thats more a design consideration than what equipment to buy.
As far as equipment I would drop the extra $20-30 and get a dual body regulator over a single body regulator - this is more for wanting to serve at two different pressures or have one for force carbing at 30 PSi and another for serving at 12 PSI, etc. Then you buy whatever manifold you need to scale up to different numbers of taps.
Bear in mind that you are need a faucet, shank, tailpiece / beernut hose and beer and gas QDs for each additional line. A good idea is to understand what goes into the assembly of the system and then plan out what you are going to need rather than just buying a "X Faucet Conversion Kit"