Hi. I'm a retired builder and developer, and I bought a few properties sight unseen. It appears that you have already got an offer. Some questions follow.
Was your property already on the market, and listed with an agent? If not, the first thing you need to do is to hire an agent for a fee to do a market analysis for you. I will be happy to help you in that way. Second, again, if you don't have an agent, you need to hire an agent who, for a fee, will review the offer for you to point out both standard industry practices and what, from an informed seller's viewpoint, should be deal-killers. Again, I would be happy to share my experience with you.
If you already have an agent, then you will have to go the more expensive route of hiring an experienced real estate attorney, who is familiar with standard industry practices. Martindale-Hubbell on-line is a useful resource. Whatever you do, before discussing your offer with an attorney, make sure that he has no conflicts of interest and is willing to sign a statement to that effect.