@Kenneth Ye your math is wrong. And as long as your using wrong math, it will keep guiding you wrong. GIGO, Garbage In, Garbage Out.
To put it into context; Your using 3rd grade math, to sort out a 9th grade math problem.
Using just addition and subtraction to sort out an algebra problem will always leave a person confused and frustrated.
Let's start with the easiest part: Selling. When a person sells a property, you Realize a gain or a loss. That is "set in stone", it's either a + or a -, there is no changing it after the fact, it is-what-it-is.
Now here is where we move from 3rd grade math too 9th grade....
When you are operating a property for rental revenue, with use of leveraged purchase money; the + or - one has on the monthly Servicing of the property is not necessarily a gain or a loss in terms of the property/deal itself, it's an Operational gain or loss.
To explain:
Say your monthly servicing is $2k per month.
And say you only receive revenues of $1,900 per month.
This leaves a -$100 per month. But is that a $100 "loss"? Maybe, maybe not. See taxes comes into play on things and maybe there is a situation where it offsets to a net 0.
But let's say it is a $100 "loss". It's still NOT a "loss" on the property/deal, it's an operational short-fall.
What's that mean? One needs to view it NOT as a loss, but like the down payment money you put on the buy, or money spent when you do maintenance and reno. It's a $100 month additional INVESTED capitol into the deal.
So how does a person know if making additional capitol contributions is smart or dumb?
ANALYSIS. Just like doing an analysis on a property before purchase, a person needs to run a full analysis to see if your INVESTING via this additional capitol contribution, or just throwing away good money after bad.
Appreciation is a MAJOR factor in this.
Say that property has a today value of $400k. And selling now locks a realized loss.
OR, a person can surf a wave of forecasted operational loss requiring additional capitol contribution of $10k over the next 3 yrs. And the forecast shows a future market value of $500k.
That is $10k investment, for $100k return over 3yrs.
I would make that investment every time.
Do you see what I mean with all this, how your using 3rd grade math to solve a 9th grade equation? You need to step back and do the accurate analysis. If you don't know the accurate forecasts, then that's where you start, getting accurate data to input so you can have an output you can rely upon.
Winter of 2011 I had a friend who was feeling crushed over his 2008 buy, and wondering if he should lock his $45k loss on it just to get out from under it due to the minor monthly operational "loss" it had. I walked him through the analysis and the answer was clear, it was well worth the additional capitol contributions.
He later sold it, years later, for a 6-figure PROFIT. And his biggest struggle shifted to pain of selling because it was now a strong operational profit.
Don't give emotion the wheel, emotion rarely steers a person straight. Math, data, strategy.
Take a step back, run the analysis, and compare scenarios. Direction should come clear.