This still costs you less that buying at market price on the MLS (I'm making the assumption that offering <80% of asking price on the MLS won't get accepted). 

I understand the person is a civilian and my entitlement would remain with the loan until refinanced or paid off.My question is if any one here has had experience with VA loan assumptions and if my plan has been done before which is:Either A: Have a clause that gives them a certain time period to refinance the loan to free up my entitlementor B: Offer more money for keeping the entitlement for the remaining 25 years. 

On any deal it is critical to understand the sponsors track record, business plan, and the underlying assumptions on the purchase.

Purchase price: $380,000 Cash invested: $10,000 Sale price: $480,000 Built a primary residence, had roomates for nearly 3 years (house hack), sold home because I will be moving soon - it was a VA loan so we did a VA LOAN ASSUMPTION!

When using the rental property calculator to evaluate a purchase, what are good numbers to use for Vacancy%, Repairs and Maintenance % Capital Expenditure % and he future assumption percentages?

Not sure if your assumption of his loan would release him to take out another VA loan or not.

@Timothy Allen when I say networth ROI I mean make sure you add into your "return numbers" the following:- loan paydown- appreciation with a 2-4%/year assumption- tax benefits of depreciating your home and getting part of the rental income tax freeI have a great spreadsheet that I can send you to help calculate all of these things.

If you change your assumptions to be more conservative, say 10% vacancy, 10% management, and 15% capex, you're close to losing money.

I will explore Urbana and Rockville but I don’t know why I have this assumption that Rockville is out of my price range.  

In my mind the cap rate for each deal can be different   And of course the next question is how reasonable are all your assumptions for every income & expense line item.  2.