After appraising my name at DomainExplorer.org and Sedo.com I have received several offers for the domain. They are close to the appraised value. But I think I can get a higher value if I develop even a simple web site? Or it will take a lot of time and efforts? How lonk it will take to get high rating on search engines?

It's not an easy thing to develop web site to earn money on them.

How close to the appraised value are the offers? Are we talking a 5 or 6 figure domain and you are just 1000 short? or are we talking 3 figures and you are a few hundred short?

I think that is good sighn for you that you have offers and I think that now you need to make good own offer. I think that domain name forums like namepros or domainstate or domainnews.com must help you