Advice from someone who has been in your shoes:

Though I'm not an attorney, I've successfully argued (representing myself) in a California court on why my ex should be imputed at an income higher than her claimed amount. She claimed $400 net per month working 4 hours weekly, and the court imputed her at $3750 gross per month, based upon all the evidence I introduced as to her education (Masters degree) and experience (college-level teaching), among other evidence.

If you look at Family Code Section 4053, subsections (a) through (d), it states that "a parent's first and principal obligation is to support his or her minor children according to the parent's circumstance and station in life."; "both parents are mutually responsible for the support of their children."; "Each parent should pay for the support of the children according to his or her ability."

The very foundation of child support law in California makes the presumption that each parent will support a child to his or her ability. What you'll have to demonstrate to the court is that mom has the ability and capacity to support these kids at 40 hours per week at her current wage.

This means that you'll have to have credible evidence that shows:

• Mom has no mental or physical condition that prevents her from working 40 hours per week.
  
• The children have no special needs that requires a parent at home, which would prevent full-time work.
  
• Mom is willful in her refusal to work 40 hours per week.
  
• There is opportunity for mom to work 40 hours per week. I think she'd have highly transferrable skills to any doctor's office in capacity of front office manager.
  
• Mom's education, experience and skills qualify her to earn the wage of $10/hour in a full-time capacity.

If you can show all that, you'll have a good shot at getting her imputed at an amount higher than $700/month. So, how do you gather such evidence?

1. Propound (i.e., send) the standard Form Interrogatories on her as a form of discovery. Among other things, it includes standard yes/no questions as to whether mom has any condition that prevents her from working, and whether any of the children have special needs. Her answer (presuming no on both) is sworn testimony and admissable in court.

2. Depose her. You'll pay for your attorney's time, and you'll pay for a court reporter's time. I think if you're only after financial issues, the deposition would be done easily within 2 hours. In the deposition, your attorney will ask her:
A) about her work experience,
B) about her intent to work full-time,
C) about her skills,
D) about her current and historical wages,
E) to list all the efforts she's made (if any) in the past year to work full time, etc. A slamdunk question would be, "Do you think that someone with your experience and skills could earn $25,000/year if they wanted to work full-time?" If she answers it with a yes, then she's pretty much agreeing with you that $25k is her earning capacity.

Your attorney probably already knows how to argue this. With help from an attorney giving me a bit of guidance, I put together arguments on Family Code 4053 (a) and (d), case law LaBass/Munsee (1997) on income imputation.

I also argued case law Marr. of Henry (2005) on "product of logic and reason" that her net income must at least equal her declared monthly net expenses (i.e., she repeatedly declared $400 net income per month but declared $3000 expenses per month). I asked that she be imputed at $3750 to $5000 per month. Judge picked the low end of that range.

Keep in mind that if you're not currently paying towards any childcare, if you ask the court to impute income at a full-time wage, you're probably going to be responsible for half of childcare costs (if any, for teenagers). In deposition, you may want to see if she'd provide testimony that the teenagers are very responsible and probably don't need childcare.

Also, your judge will have the discretion to impute her. I've been told that some judges will mostly impute full-time at minimum wage (i.e., no one can argue that every adult should at least earn that). I've also been told that it's rare for custodial parents to have their income imputed in order to reduce child support.

The weak counter argument that your ex's attorney may raise is case law Marr. of Cheriton (which my ex argued), which found that it is not in a child's best interest to impute income for purpose of reducing child support and hence have negative impact on the custodial parent's ability to care for the child. My response to that is that if a parent actually WORKS full-time, total support available to the child would be far greater than if the parent refuses to work and only collects child support. In my case, the judge didn't even hear oral arguments. He just announced that my pleadings convinced him that mom could earn $3750.

This is purely a cost/benefit analysis for you. To properly prepare for your motion to impute income for mom, it may cost you a couple thousand (i.e., attorney at deposition, certified reporter for deposition, and preparation of pleadings). Have your attorney run some Dissomaster numbers on what would happen to your child support if mom is imputed at minimum wage and if she's imputed at $2,000/gross per month.

If your best case scenario is only a decrease of $30/month, then it ain't worth it. In my case, my child support obligation went down $150/month, and my child is only five years old... significant savings over the next decade; and also sends the message to mom that she needs to find a job and help support our child.

If you're doing all this without an attorney, you're going to need to get some help with how to depose, file, and present everything. You said that you're already on calendar for July. I filed an OSC to modify support and impute income, and it was accompanied by my declaration and points and authorities. In the past, I've hired a prior attorney on an hourly basis to review all my forms-- she was fine with meeting with me for 60 to 90 minutes every once in a while, and I paid her the hourly rate to do so.

Income of a "New" Spouse?

While the income of a subsequent spouse is not considered in determining support levels (§ 4057.5), it is relevant for purposes of section 4059. That is, "the income of a new spouse must be 'considered' to the extent it is necessary to determine the obligee spouse's actual (and appropriate) tax rate." ( In re Marriage of Carlsen (1996) 50 Cal.App.4th 212, 219, italics omitted.)