All assets and income are relevant to standard of living and ability to pay.
DISCLAIMER: I am not your attorney and readers employ any information provided herein at their own risk. Any comment is for general educational purposes only, and is based only on the limited facts provided, which may or may not be true. It is not legal advice upon which you may rely, as the commenter has not interviewed witnesses or examined any evidence, and has not researched the applicable law. Available defenses may prevent the success of any claim. Competent legal advice should always be obtained from a lawyer licensed in your jurisdiction before taking any legal action or filing suit.
There's a formula - contained in the child support guidelines - that determines child support. The result of the formula is presumed to be the proper child support amount. However, a judge can change that amount if he decides there is a good reason for it.
The formula itself contains a large number of different line items for income and expenses. You can see the worksheet for the formula by visiting: http://www.dphhs.mt.gov/csed/packet/worksheets.pdf
There is also an online child support calculator at http://www.mtchildsupport.com
Be careful of other online calculators since they aren't based on the Montana Child Support guidelines.