The foundation of this comes from the loan- your knowledge of the loan.

There is no "secret" that the big boys are doing necessarily, just incremental pieces of information, relationships, and knowledge that have been built up over time at scale. 

This community is full of helpful resources and knowledgable professionals eager to assist during your journey.Have you chosen a brokerage yet? 

There's no true data source that aggregate all the data that you look for (at least to my knowledge).

Definitely there is a lot of opportunity for him to learn a lot from this property if he is receptive to acquiring the knowledge.  

Is it better to find one that's close to where I live (Fairfax, VA), or one that has knowledge of the local jurisdictions that my properties will need to adhere to?

Never underestimate the knowledge of a local!

I actually had an initial phone call with the co-host that ended up lasting an hour because he kept giving me tips and local knowledge.

I am in the research phase and not in a huge rush, but some great points ,advice, and knowledge in this thread so as a whole, THANK YOU! 

Milton and Farmington can be excellent choices, too, often with more budget-friendly options and the chance to add value in less saturated areas, might have better cash flow luck here.For lenders and agents, I'd recommend networking with those who have experience specifically in the NH Seacoast markets since these towns can vary in terms of tenant demographics and rental demands.