@Mohan - I too am sorry you are in this spot.
Re selling, you don’t have to answer this in this thread / publicly online, but consider the price range you are selling. If it is less than $10k, then probably something very simple will do.
If it is $10k or more, you need some protection in the contract. The buyer is buying “as is, where is”. No promises on your part of suitability or even soundness. Etc. You are forestalling anything an unhappy buyer may do. Most buyers may not take action against you, but it only takes one unlucky hit.
You may hear/read a lot of advice about people who have sold horses for 10 or 30 or 50 years and never needed a real contract. That has nothing to do with you yourself and the present day & age.
You can take a look at online horse sales contracts to get an idea. If your horse is very very expensive, it may be worth a few hundred in selling costs to get an experienced >>horse expert<< attorney to draw one up for you.
This is the kind of thing to do in your own best interests. You really need more qualified advice than the internet provides. And if someone is giving advice, consider how much stake that person has in the outcome, and how much they know about your personal situation. Which you do not have to share on the internet.
Good luck that this turns out well for you and your horse. 