I am preparing to file for divorce. If I separate from my spouse, and purchase a home, is it community or separate property?

In Illinois, when you are going through a divorce, property is classified as marital or non marital property. Marital property is anything which you acquire during your marriage, such as the house which you are about to purchase. However there are exceptions such as property which you obtain during the marriage by gift. That would therefore be classified as non marital property. The significance of the clasification between marital and non marittal property is that with non-marital property, you get to keep that upon divorce. With marital property, you spouse may be entitled to a portion of it (not necessarily 50%), depending on a number of factors, including the value of the property, the length of the marriage, the contribution the other spouse made towards the acquisition to the property, the relative income of the spouses etc.

You should consult with an experienced divorce lawyer, to determine specifically in your case, taking into account the factors I have mentioned an others, whether your husband really would have a viable claim to your new home.