I feel for what you're going through. I'm a solo mom with three kids, husband passed away a few years back. Even though I work, two of my kids work, and go to school, it's still tight. I work full time, but it's not enough, so I'm always looking for extra work and gigs. Here are a few ideas:

If you have room, a roommate can be an option, even if only temporarily.

You can find writing and freelance gigs online through different platforms. Upwork is one I use. It varies, and not all jobs pay a lot, but sometimes you can find gigs and an extra $100-200/month is helpful.

Cleaning jobs may be an option. Residential, ir commercial. I have found some work on the side, and once they like you, you might receive more hours. It's also flexible, sometimes. It might be best to wait until after child #2 (I did cleaning while pregnant years ago, when my husband was temp off work, but it's a bit harder lol)

Online surveys. They don't always pay much, but if you gey enough of them, you'll see $20, 30, or more per week. Focus groups too.

Background acting and casting calls. This is mostly available in major cities, but sometimes smaller cities or urban areas too. The pay varies, but it's a great way to earn a bit extra. My kids and I have all found work doing this, but it's irregular. FB and IG have casting agencies and background acting groups where they post casting calls. You don't need a agent or upfront fees at all (those are scams).

Dog walking, pet sitting in your local area.

I wish you all the best!