I learned at simpletractors.com, its called the bent screwdriver trick. One of the shifting forks may be stuck. I fixed a 7016, this may be the same. You need to see if there is an inspection hole. Next you use a screwdriver to follow the two rods, one will have a shifting fork bound. Of course it could be an all together different problem. Those little guys go for 100-200 in running condition and the blowers are not a big add on in price. I bet you could find a good running one with a blower for 150 and not worry about it.
I think it looks generally neglected and probably needs a good go through - most of that a fairly easy project. So, do you want to do tranny work?
If you are willing to take that chance, I think the price is a desperate reach - and is merely an ask for a true price of $100. And possibly less than that. I think the blower helps to prop up the price; but it is pictured growing weeds. And I think, overall, it has been run into the ground; and owner is no mechanic. I wonder about deck bearings also. But the big problem might be motor if it won't run. This one has ALL the usual risks with a bonus challenge.
If you want to play in the shop for a few weeks, it could be fun.... for a low price. And you could argue that you could resell or part it to recover investment, if all goes down.