I wanted a homebirth BADLY but United would only cover a CNM out of network for me, too. They make it VERY unceonvenient to have a homebirth as far as I see it.
First of all- dont mention it's a homebirth or ask if they cover homebirths. It doesn't matter WHERE you birth rather who attends you.
In portland the miwdwivery cost is mainly attributed to the birth, however the total cost covers all your visits minus Ultrasounds and labs, etc.
I have to have monthly labs and Ultrasounds now and then do to a blood issue I have where I have an antibody to a gene trait my husband carries. So that already brings the cost up for me. On TOP of that I was already seeing midwives at the hospital here so I was in the pot with them as it was. Most the midwives required full payment by 39 weeks.
So- my advice is this: Find a midwife who takes United who is flexible in receiving payments after delivery and start using her ASAP. Sometimes billing them is a pain in the butt for them- so it's great if they already are plugged in.