My question is how do I evaluate if this sale price is the right? 

Your right about the margins being thin, and even after all of the math and work we have put into evaluating this opportunity, I am just not sure $10k-$15k would be worth the risk (especially on our first flip), so I appreciate your feedback for sure.

The key is knowing the difference between a motivated seller or not, from there you can evaluate the deal.  

Here is something to try to evaluate the doublewide.https://www.nadaguides.com/manufactured-homes/valu...

How many log in daily?

But I dont think using comps to evaluate the property would accurately represent the buildings current value. 

Many people might argue with me on my next point, but I would suggest that you pick up some skills in the "trades" so you will learn more details about buildings and be able to evaluate buildings more clearly. 

We spent the 3rd quarter evaluating the market and houses. 

Of course the forums and podcasts are great resources, check out the "Analyze" section for some cool tools when evaluating property. 

Separate the commercial from the residential when evaluating.