I found a Hercules 3 speed that's in ridable shape, but a little rough around the edges. The seller wants $50 for it. I have no idea if this is reasonable or not. What should I consider with this bike? I'm not sure of the year.

Without pix, & better description, it is hard to say what it is worth . Are you wanting to fix it up to ride,,, or sell ?? I try to buy most any English 3 speeds, though.

Is it an AMF Hercules or a genuine Birmingham Hercules?
If it is a genuine Birmingham it will have a "Hercumatic" shifter and hub. At first glance they are dead ringers for the SA shifter and hub, probably made by SA. I don't think the Hercs were date stamped like the SAs
My Herc went back to the early '50s. I don't know when AMF got into the picture.
Price depends on condition and how much someone wants it.
My guess is about $200.00/250.00 if it's in really good condition and all original.

Hercs from about 1960 and on used SA hubs (Raleigh bought them out around then. I have a Birmingham-built Herc with a SA AW hub.)

I asked the guy if it was any identifier on the hub, and if there was any notation that it was a Birmingham. It appears to have an original (and gently used) Brooks saddle on it. There was some light rust, but I don't recall anything bad.

So is the Birmingham hub a good thing or not?

Oh, and I'm wanting this for a around town kind of bike. Kind of another choice depending on my mood. So I'm not planning to put a lot of work into making it look nice.

If it's got a leather Brooks in decent condition on it, then the saddle is worth about $50 alone. Bear in mind, though, that Brooks also made vinyl mattress saddles.

If it has a Brooks, it's probably post-1960; Brooks was a Raleigh company.

It seems that everything involving the British bicycle industry eventually came under Raleigh ownership

The guy decided not to sell it after all. It was the SA hub.