If the bike has 11,000 miles (or so) on it, the splines are probably still ok, even if they are (still) bone dry.
Personally, I would not worry about the splines being gone unless the bike has 15,000 miles on it--or more.
In any case, you'll usually have to inspect the splines yourself after you buy a used bike. Very few owners will be able to substantiate that the splines are ok, before you buy.
With spring time is just around the corner, it is still very much (and will continue to be) a buyer's market in the motorcycle world here.
Even though gasoline prices have shot well past $3/gal and will probably climb higher before they come back down, most people will still want to drive (rather than ride) when they need to commute to work, get groceries, etc. I think this is crazy, but nonetheless true.
So...most people who shop for bikes will still be bikers, and not really anyone else.
The real point I'm trying to make here now is that if you have real doubts about a bike, then forget about it and keep looking. There are too many remaining VN750s out there to settle for one that you don't feel good about.
With all that said, you can usually tell if a bike has been well treated (or not) buy giving it a good visual inspection. A bike (as opposed to a car) simply can't hide good care (or the lack thereof).
Sometimes, you need to look closer, though. I once sized up a used Honda Shadow VT1100. I walked away from the deal, because...upon closer inspection....there was rust on the inner frame where the battery box had leaked battery fluid/acid. The damage was irreversible, and would only get worse with time. A more casual observer would have missed this serious problem, I think.
Other threads exist on this forum that explain what to look for with a used VN750. Use the "search" function shown above, find them, and read them as your schedule permits.
Then....feel free to ask questions as needed.