I understand r-values and all that stuff. That said an insulation
person inspected my house and noted that the underside was not
insulated (my house sits off the ground about 3 feet. He suggested
foam insulation and quoted me $1.50 per square foot for a cost of about
1500 to do the job. My question is that on the web there are plenty of
spray on foam insulation products with DIY equipment. Seems a simple
enough job.

Is this something that can be done by one's self? If so which product
would you recommend?