I have two sites that need SSL for entering payment and account information, and there will be a third in the not too distant future. If I get a VPS that says it has three seperate IP addresses, then I can host the three sites with different SSL certificates right? since they're bound to the IP address... (they do need separate certs... or at least two of them do... might use one cert for two, and then another for the third.)
SnapOverflow
Yes, as long as you have one IP address per site you need to access via HTTPs you will be fine.
Though you will not be able to use one certificate for two domains unless they are sub-domains for the same domain and you get a wild-card certificate.
It is possible for multiple sites to run HTTPS off a single IP address if you use Server Name Indication, but this will mean users of older browsers have trouble with your sitea so I wouldn't currently recommend it.
That is correct. You need a separate SSL cert per IP address. I believe that more and more browsers are working with certs that specify Alt Names, but for the greatest compatibility, you should do one per.
Yes you can, assuming you are talking about Apache:
The best option would be to have mutliple IP addresses and do IP based Virtual Hosts. It is possible to do name based virtual hosts with ssl by using mod_gnutls, but I would opt for IP based because it might not work with older browsers.