Leo,
Most hosts will provide you the means to have a secure site. The host will probally charge you a small extra fee to have a dedicated IP (required for SSL) and possibally a setup fee. Then you have to buy a SSL certificate usually about $35 and up.
http://www.freessl.com has nice chained certificates and ev1servers.net sells Geo Trust certificates. I think the chained SSL is the same as Geo Trust.
If you do any credit card stuff on your site or even collect sensitive information about your customers it is your responsibility to make sure that information is kept secure and not compromised. Not only are people steeling credit cards off the net but there is a lot of identity theaft going on as well.