It really depends on how high quality the trunk line was when they put it in, if the cable has any sharp bends in it which can cause cracking (not just in the outer sheath but in the copper wires as well) and how fast the cable is degrading etc.
In this forum we have several instances where the trunk line was fine but the line from the trunk to the nid outside the hoses needed to be replaced or the line from the nid to inside the house etc. needed to be replaced.
Your distance from the home office plays a role in what sort of speed you should expect. To get the fastest speed you need to be a mile away (5000ft) or closer. I'm at around 3 miles away and I get 3mb/s down. (I don't have the exact length.)
DSL is mostly unlimited but Frontier does occasionally warn the top 1% of users if they are downloading 24/7.
If you have a local phone book you might be able to find it in the white pages.
Once the system is installed you usually have a 30 day window during which you can cancel the service.
If you are looking at 10 miles that is going to be too far away (50,000 feet) unless you are in a subdivision and they put a remote out there. If you have any neighbors ask them if they have it and see how well it works that really is the only way to know or sure. (speedtest.net is not perfect but it gives a good general idea of speed)
I don't have have a active phone line (for 10 years) but plunged in a few random numbers I know that are local and it found a Wire Center 8.7 miles and another 6.7 miles from here before I hit max search's/day.