How to know real value of a domain

[BluePearl]

Hey just found out my 18 yo daughter is about to have a baby and
want to try and make up for lost time
Need to know if what I have is worth selling now
and how to get an accurate value prior to selling
I don't think dnscoop etc is what I mean
any feedback is appreciated the one site is the hottest blogging
community on the PLANET and my own semi popular MAD links POT BLOG
Let me know if you have any advice I need to be there for my kid
Thanks