I believe there are some pretty good tutorials that will teach you what size your models should be. In essence, the size should be decided prior to game development and used for all art you create. I mean, who wants a crate model twice the size of the character. Nagshi (who isn't a very active member anymore) had a great Max/Med conversion for size video tutorial, a very good watch if you can manage to find it.

However cerberi is correct, starting out with a Max Payne type game has a very low percentage of actually working out as you want it to. It's best to learn the programming first in small steps. Become familiar with everything, even work with a small developing team you find in the Jobs Offered forums and learn how it can be to work with a small team - even if the hopes of the project itself are low. You'll learn a lot.

Either way I wish you the best of luck.