Welcome to the forum! Check into google planimeter . If your potential pond has been around for a few years it might be on there. You can use it to measure the actual acreage of the pond. Pictures are deceiving, but to me it doesn't look like 3.5 acres.

If you do get the place, what do you want to change in the pond?

www.hoosierpondpros.com

[Linked Image from lh6.ggpht.com]
http://www.pondboss.com/subscribe.asp?c=4
3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).