Do I need to have my dad's small vacation property legally appraised?

My dad has been in a nursing home for 2 1/2 years. We are told that he will qualify for 'benevolent care' after 42 months, but in order to do so, he needs to sell his property first and be down to his last $2000. I am interested in buying his small piece of vacation property. There is an old trailer on it with electric and propane gas, but potable water must be carried in-no well, and no room to put one in. Do I need to have a certified appraisal, or is it enough to pay double the SEV from his tax statement? I'm told that at the time they decide whether he qualifies, they will determine whether the property has been sold at a fair price. To pay an appraiser would be an extra expense that we really can't afford on top of helping to pay for his care in the nursing home at present.