If you can afford it, buy the stihl or the husky 50cc pro saw. Then you will learn what a proper professional saw feels like.
It will most likely be your most used saw. Then expand your line with whatever you feel like.
Until you know what a true pro saw is, you will never know. You might come on to places like this extolling the virtues of not-really-pro saws as if they were. Not knowing.
If you set a high bar, you will be able to accurately assess other equipment, and determine if it will satisfy your requirements/expectations. And many sub-pro saws will, over time. I like the ms261 suggestion over everything else suggested.
Life lesson...
Good luck!
I would buy a chinese saw over any of the big name farm saws for 1/3 of the price or less. But I would buy a professional stihl or husky if I were you.