Hosting and rackspace matter a WHOLE lot if computers are central to your business. Would a bank get started without a vault? Can you build a house without a foundation?
The point is as cheap as possible... not as cheap as cheap...
If you're going to end up with a lot of servers: get into rackspace NOW and develop a relationship with the datacenter. If computers are at the center of your business then you owe it to your business to house them with the same care you would your employees.
Or, you could grow it ad-hoc and deal with serious downtime and expansion issues later and attendant costs. Choice is yours. I would consider how well you like stress before deciding.
Convincing people to use their own computers is epic fail if you have intellectual property issues (or think you might in the future.) If your employee is going to sign an NDA under no circumstances should you allow them to use their own computers.
Also, varying degrees of attention are paid to things like vulnerabilities and stability as well as standards. If your relying upon yourself to do IT, then you're automatically setting yourself up for connecting ten different computers in 15 different ways. This does not scale.
Then of course, you'll have the hotshot programmer who'll set up his own sourcecode repository and you'll have no end of headaches getting the two repositories to agree. If you're going to rely on computers with minimal IT staff then you need to go cookie-cutter approach in the beginning and set up definitive rules like "a server is a server" and "a desktop is not a server".