The way I would look at it would be as follows:
You can get a half decent desktop which does not require top of the range CPU / Graphics Card as it will only be used as a server, once running - it does not even need a Screen. A Pentium 4 2.8 Ghz or an Athlon XP as long as it had at least 1 GIG ram would do - many of these can be found on E-Bay @ £50. The machines I have found to be Quiet and does the job seems to be Dell GX260 for example (or any dell range, they all seem whisper quite to me)
Initially you would run the server from your Existing Broadband connection and depending on the numbers playing, the server should not lag, not make much noise or steal too much of your bandwidth. If the server then picks up to a good number, you can buy a ADSL line (if you can get this in your area) for the lowest price possible, does not matter about Caps as you will not be using that much per month.
Further to this, when you hit 150+ Playing, then I would suggest a Dedicated for the Bandwidth - remembering that the main number is Upload. In regards to Donations (as this subject is be battered to death at the moment):
If people donate with the upkeep of the server as they see fit, then this is up to them and also up to the host to what they spend it on, whilst running it server uses up Bandwidth, Electricity and so forth, it was the Host's Choice to run a server in the first place and should have taken this into account. I would suggest the host have enough money to pay for at least 3 Months Dedicated and maybe already getting Donations before moving forward to committing to Dedicated in the first place - this is one of the reasons Servers keeps going down / Loosing Database's etc.
My Last point I guess is the purpose of Private Server Files - this is a Hobby to run a server for your mates or you feel you have a lot to give in regards allowing complete strangers play your own Server. In order to keep pushing the Scene forward requires some giving as well as Taking. If everybody stops doing this (which it has - no sign of any V5 Server files on this site is there), then it will slowly go down hill much like Woool for example where even though there is only one server online (of sorts), it has Zero Users online 24 hours a day,.