If you do at the end of the day all you'll have is problems and headaches with no rewards.

-rent price: this is where comparibles come in handy for the area-margin: rent minus monthly costs.

lot going on in this post.first, no way will you get a 5.5% on a non occupied investment property.(2) you *may* end up with positive net income on the property without having the mortgage writeoff - this means a visit from the tax man. as an investor, the "write offs" or tax deductions you will receive, if your business entity is structured correctly and your CPA knows what he/she is doing and you keep tabs on it, will far exceed any write offs you will earn anywhere else...look at it this way...IF...you HELOC...taking 100k out of your property...now you've got 100k to invest in an reo or other distressed property - CASH...real estate is about leverage...but with the CASH purchase, it frees you up to do many different things down the road...IF...you "buy right" (below market value > 30%) - combined with the CASH purchase, you'll create a return on your investment that is EXCELLENT.if you took an arbitrary 100k (from anywhere, say it grew on a tree) and you stuck it in a savings account earning 5% (which is a lot for a savings account)...compare that to the 20% return you'll get off the monthly cash flow from a good rental...not to mention depreciation..and future leverage options available to you through this investment...the returns just compound.now this all deserves a qualifier...we don't know the specifics of your current home, your finances, what you owe on it currently, other debts etc.all that must be taken into account.

I get all the information I can from the seller and I figure what I think all the numbers would be from my experience, and then I compare the two and come up with my "numbers" to figure off of.

I am sure you can find relatively intelligent people on both sides that will tell that their way is the best way, but it does comes down to balancing your personal risk versus reward comfort level.

Find comparable sales (you're doing this)2.

I would want to know what the rent will look like compared with the total debt you'll have on the property.

You might find comparable houses or apartments for sale and see how yours compares.

Then I will go through the list and find a comp price, and a market value price for the prop, and use these to compare at time of sale to help our choices..

The problem is that in most cases comps could be interpreted both ways, supporting the price and invalidating the price.Comparable sales are always the most accurate way of determining fair market value, but when you are picking two or three out of a hundred to compare the subject property to, discretion comes into play, and with it human error.