Joe, to your last question the answer is yes, and so can Mac users. And whoever has the password can alter any contents, no matter what system they run. Only if they want to test the software meant to run on the server, it is sometimes necessary and often advisable to have a similar system for testing.

Basic services including a domain name, a couple of gigabytes, script languages such as PHP and Perl, and a basic database management system such as MySQL, should be much cheaper than 10$ per month. Additional features, high performance, and large traffic can be more expensive - pay for this only if you need it. Jon seems to be an expert, I am not.