It's calculated by dividing the NOI by the property value.While cap rates provide a quick valuation metric, they don't account for future income streams.

there are really good calculators out there based in excel spreadsheets

After the last refi the new mortgage loan was $170k and sold the house for $270k so I thought I was going to owe on a gain of $100k but she says I'll owe on a $180 gain because she's calculating on all 3 gains. 

I didn't know that I had to sign up this forum to talk with you.There are several things that I would have done if I were you:First, calculate how much your monthly income and expense.

If you are using rental income and you already filled your taxes with those rental properties then they will use the your tax returns and schedule E to calculate your income.

Any idea how to go about calculating how much tax I'd owe when I sold the land?

Play around with this calculator a bit https://www.ipx1031.com/capital-gain-estimator/Agree with @Greg Scott. 

At the end of the phone call I told him it would be more than $16k to redeem & I needed to sit down do a calculation on the exact amount.  28 minutes later I texted him my calculation (taxes plus interest + value of repairs plus interest = $20,549.76) and asked for him to provide me with his mailing address so I can send him a formal notice of the cost to redeem by certified mail.  

What kind of returns is your calculator spitting out?

New to the BP community and looking forward to learning from you all.Honestly this is a really simple calculation, the main reason to buy a primary residence is to shelter yourself from increasing rents, the breakeven timeline can vary greatly on that I’d play around with a calculator like this (https://www.calculator.net/rent-vs-buy-calculator.html) figure out how long you your break even is, how long you think you will be in area & make a decision based on that.