CAP rates are only one part of the evaluation tool. For instance, I would buy a park with a 2 CAP if it had upside, and I have walked away form several 20+ cap parks. To really evaluate correctly you should use a program called an APOD. You should also project ownership over several set of timelines, like 2 years, 5 years and 10 years. Calculate your return with a 1031 and without. Also calculate as if your an IRA and not. In that APOD you will see the CAP, but also the rate of return, internal rate of return, the cash on cash return (which is ONLY good for the first year), and then you project out using return on equity. That is the real telling number. Some programs will graph and track the year you should sell for the highest return.
In the APOD analysis you should be able to break your income into differing streams. As Frank said- you must separate the streams. This is where you value the homes but do not cap the income. You can have a 10 CAP park with a 30, 40 or 50% cash on cash return... or a 10 CAP park with a 10% return.
Lots of moving parts to a parks valuation... do not get hooked on any one number.
so there are several places to get the software. I have some I have collaborated on building and some off the shelf options. The off the shelf option I like the best is from http://www.rentalsoftware.com/
I really like the reports and use this software when I buy, and also as part of my package when I sell. I use both the analysis and flippers software, as I can project upgrades, costs, evaluations etc.
I am not affiliated with the company in any way, shape or form. I just like the product.