Doesnt look too bad for a large frame skid steer. You didnt mention how solid the rock base was. A tooth bucket would be mandatory. A ripper attachment May be in order.
The only part that concerns me is your buying a machine site unseen. Add to that you say you are on a limited budget, and that could be trouble. When these machines break down, they are expensive to repair. If you get it cheap enough, and can absorb that cost in the resale, that is a win. Often times, thats not the case. In order to do that, we often have to buy a machine in need of repair and super cheap. Are you wanting to do that, or just buy a skid steer turn key and go?
Is there anyplace there that will rent you one? Usually rentals arent a bad choice for doing just one job. And, you can add insurance for breakdowns, otherwise, they are on the renter. Around here, they are around $1000 a week.