First, most colocation charge by space in the rack, so towers are not a good idea..You want a 1U unit.
Second, you pay for the space ( let's say 50.00 a month for a 1U).
Third, you have to pay the bandwith.... Most colo give you a choice of a connection ( 1, 5, 10 etc...).
You are responsible for your hardware failure
Control panel licences are more expensive, if offered
If you compare the bandwith price of colo to the price of a rented server including BW, you will see that the rented is cheaper...
The advantages of colo are not really the price as such ( if standard) but:
- Access to the actual server
- Upgrades are cheap, because it is your server ( memory, HD, etc )
- Easy to load content if big updates or new site.
