If one side has too much weight, you'll go up in the air or crash down.

This usually happens in cash transactions, where no loan is used.So, generally speaking the buyer can use the appraisal for whatever they want, but, if it used for a different purpose than what it was intended for, it doesn't hold the same weight.

I'm not sure what her "science" is for landlording but I'd want to find out to avoid buy a $90k paper weight.

In my mind, I would figure the rental income the property is producing would have more weight with coming up with an offer but my realtor states it's more based on previous sales and comps.

At least that's what I do with my investor clients, and any LO worth their weight should.If this is a 3 or 4-unit property, now you are going to be stuck in that 203K loan for awhile.  

Is it the old windows with led weight?

This is because the IRR considers all monthly payments in the amortization schedule even if they are different by taking weighted averages over time.

Lowes sells the Pella brand -- I feel they're not as well made.I pay about $170 per replacement window and I can remove an old double-hung window, remove the weights, insulate the weight cavity with rock wool or fiberglass insulation, and put in the window in about 2 hours each.

Most of the windows that need repairs just don't slide like they are supposed to, the counter-weight system seems to be messed up in a lot of them.

I would look at what the trend of average rent increases have been in your market over the last 10 years, I wouldn't put as much weight in the last two because they were so unusual.