We had access to one and were about to sell but the irs told us we had to pay it all IRS has nothing to do with property taxesIn addition at death the taxable value is adjusted to the value at time of death. 

Then plug that address into the platform/software you use to pull up additional comps for similar properties.Realtor.com and redfin have a ton of free data as well.

For example, the house is listed for $500k and it has $300k in mortgage left at 3%Could I offer $500k and "assume" the mortgage of the seller?

It's an excellent addition to David Green's book "Long Distant REI".

If a duplex rented out for 2k per unit, would adding another unit be an additional 2k in rent, or would it dilute the property and make the rents lower. 

However, I get people asking for a monthly rental all the time, so we offer it with a 25% increase to the normal rent.

What is the best cash offer  i can bring to the table since the owner want his equity and does not want to loose the home either.

I was losing my offers to mostly all-cash buyers, and also they were going higher than I wanted with their offers (usually because I had a ROI in mind) - I was not smart because I think I was thinking the low rates would last a while.

I've spoke with the folks over at Abodea, who do offer a scalable call-center approach to HOA PM at quite affordable rates, but we're still missing the kind of local, on-site general contractor/handyman or capital management planning schedules that would be required for proactively addressing homeowner and community association needs. 

it seems like they usually only deal with larger companies that have many accounts to offer