Yes ...it's part of the due diligence. Who is your competition (including apartments), what are they charging and what point of differentiation/competitive advantage will you and your park bring to the table? I wouldn't fear competition, but i would make sure i have a crystal clear understanding of what the competition is doing and make sure i can deal with and/or beat the competition, whether based on price, location, quality, etc.
We have two parks, and there is significant competition in both cases. But we also knew going in that the price we were buying at allowed us to -- if necessary -- significantly underprice the competition.
There's no reason to fear competition as long as you fully understand your and their points of strengths and weaknesses.