There are established general rules that apply to heterosexual marriage and divorce. Unfortunately, these rules are new to LGBT couples entering civil unions. They are important and everyone who plans to "tie the knot" should be aware of them.
If you enter in a civil union you need to be aware of what you may have to pay for if you split from your civil union partner. First there is maintenance formerly known as alimony. The amount and duration of maintenance is determined based upon relevant factors including age, income and property of each party, education, length of the civil union, whether the recipient's ability to earn income has been impaired due to absence from the workforce to attend to domestic duties, and lifestyle of the parties.
Second there is child support wherein a civil partner may be entitled to child support for the children of the couple. In most cases a percentage of net income guideline child support is 20% for one child, 28% for two children, 32% for three children, 40% for four children, 45% for five children, 50% for six children.
Third you will have to pay attorneys' fees for yourself and you may have to pay the legal fees of your civil union partner. The law says that attorney's fees are the primary responsibility of the party incurring fees. However, if your partner does not have any money, you may be required to pay his/her fees. Contribution of attorneys' fees from one party to the other is available where the payment of attorneys' fees would undermine a partner's economic stability.
Finally, before you enter into a civil union you might want to have a Prenuptial Agreement. Prenuptial Agreements clarify the rights and expectations in the civil union and can reduce the expenses and stress in a divorce by eliminating the issues to be determined. Prenuptial Agreements must be in writing and signed by both parties. They must be must be entered into freely and voluntarily. And they require fair and reasonable financial disclosures.
I have always advocated for all parties in an LGBT couple to create their own property agreements and decide what issues should be covered such as: what is civil union and non-civil union property, who gets what in case of death or divorce and define establish, limit or eliminate spousal support.