The broker is telling you how awesome the deal is and you want to get one under your belt, so you convince yourself that the market will keep increasing in value at it's current speed. 

After having the property inspected you should be able to project a more accurate estimate.I would increase the amount for Maintenance for now.  

We had a potential tenant who was late on multiple things and was wanting to increase her rent from $800 to $1300 to move into our place.

I always removed the additional income because I feel I should not value a property for lost key fobs or pet fees.Also, when it comes to Expenses I left the expenses as is and mostly increased the management fee from 2% to maybe 3% depending on the size of the deal and I always adjusted the property taxes.Is that the right way to quickly value a property? 

I recently bought a house for $800k and that uncapped the yearly property tax increases and now the projected property tax assessment for 2019 is around $805k!!! 

Ideally the rents would be under market with the units as-is, or under what you could get after relatively minor updates to the units, giving you an opportunity to increase NOI.Of course the expenses in the listing are only $9,784 per year - in listings they are always going to be low, to inflate the NOI. 

Then you can rehab, raise rents and actually increase the sales price!

We have already increased our knowledge through all the great information available here on Bigger Pockets and look forward to continuing our education.   

With our current debt snowball plan we will be debt free on all of our existing rentals in just over 7 years (even if we never increase the rent - which we of course will be doing).

If you are satisfied with your IRR, based on ability to sell in 10 years, depreciation, possible appreciation, possible rent increases and debt pay down plus your rental income, then you buy the property.