Given the dictionary definition, I take upscale in this context to mean "a man of means." The opposite of "a low rent MF." We all know what's meant by generous. So basically, a dude with plenty of cash to spend who wants to spend it on the ladies. Preferably the one placing the ad. "Respectful" is often used in these ads as well, though I imagine an upscale and generous fellow can purchase a pretty fair amount of leeway in regard to the respectfulness issue. That's been my observation over the past half century, anyway.