I am new to horses also, been taking lessons for about 5 months, bought my first horse at the beginning of February. I couldn't be more pleased with my experience so far! I wanted to share the events that led to where I am today, because I believe that things couldn't have happened any better!
I started taking riding lessons at the end of October 07. My instructor had me riding different horses at the barn so that I could see what differences there were in horses gaits, personalities, etc. as I learned. Having experienced many horses, I better knew what I wanted in my horse when eventually I started looking.
By December, I had become comfortable enough with my instructor that I asked her to help me look at horses. I started looking at all those .com sites and visited a few horses. She was willing to help me find the right horse, and I volunteered to help at the stable in return and purchased a few lunches/dinners.
As it turns out, people in the horse world know plenty of other people in the horse world who sell horses! I ended up leasing a horse that a reliable friend of hers had raised and trained for a month and at the end of the month I purchased him. I am also boarding him at the barn I have lessons at so that of course I use him for my lessons, but whenever I run into a problem with him, I have expert people to help me out!
I would definitely say for a beginner, that leasing the horse for at least a month beforehand is a GREAT idea! I think any reputable person who cares about their horses and their buyers would definitely agree to that. In fact, the person who was selling my horse probably wouldn't have flat out sold him to me after watching our first ride (he likes to find a good match!)...another good sign!