Hi edag and
Good call on taking some training. Is it the MSF basic riding course?
A good starter bike is probably going to be something in the 250cc range such as a used Nighthawk. Or a small dual sport is nice because then you can practice in dirt too (supposedly riders with dirt bike experience have less accidents on the road).
There is a reasonable list of suggested starter bikes at
Introduction to Motorcycles Often people say buy a small used bike, then after you have ridden it for a while move on to something larger if you want and sell the small bike (or keep it!).
I started on a Honda CRF230L dual sport (17 horspower), which was an excellent starter for me, very light, low seat, super friendly to ride, works nice on road and off, yet can go 65mph no problem, plus gets like 75mpg. Then I got a viffer which I love, but I don't think I'd have done well getting that as my first bike as it is much heavier and farrrr more powerful. If you have a short inseam I think a viffer would be even a less suitable first bike since its seat height may not allow you to flat foot it at stop lights.