We are discussing divorce and are interested in mediation to avoid excess costs and animosity. We own a house and I'd like to know if we should put the house on the market before we begin mediation.

In a mediation session, we might consider various alternatives regarding the house. There might be an option in which it could work out better financially (or emotionally, for the kids) if one of you were to remain in the house. Because no decisions are absolute yet, I would recommend that the house not be put up for sale until the three of us can look at the whole picture.

<<...to avoid excess costs and animosity>>
Of course the cost, but especially the animosity. Mediation provides an approach to making all of the decisions related to your divorce, with a charge of not making things any worse than they already are -- and maybe even improve the relationship. Your children need to see that the two of you can be ok with each other after the split-up.