Echoing others here that this is a very risky plan. I lived in LA for several years in my twenties. It's fun but it is wildly expensive. I can't imagine making a move to a city like that in my 40's unless I didn't care about FIRE or having children or owning property in the area. But if you do go, there are a few things I suggest:
1. Use the trains and live near one (outside of biking and walking which you can do year round). They are building trains right now that run through major parts of the city. It is very spread out so you may still need a car but if you put your mind to it trains, biking and walking should cover you most of the time if you work from home.
2. Don't go there to follow an acting dream. And just because you live there doesn't gaurantee you anything. Go because you want to live in that city and call it an adventure with a time limit. Lots of talent there, very difficult to break in and it could be a long time - if ever - before you actually make any money doing it. On the other hand, I know people who have made some nice side cash as extras on sets and game shows. Maybe network and meet people there and everywhere - one chance meeting could get you everywhere in LA. Echoing the scarcity of work for women in their 40's across the board - careful!! Maybe have her get somewhat of a current resume going before you leave. Local shows and such??
3. At one point downtown LA lofts were priced better than popular places like Santa Monica, Hollywood etc. Not sure if that is the case now but I would start there or maybe Silver Lake. You could always live in the valley and travel into the city whenever you get any gigs which I suspect will be few and far between for a while....no trains there though. Roommates would also help with funds although I wouldn't do it personally at that age given your situations with kids etc.
4. Craigslist is very easy to use out there and I used it quite a bit. People are always moving in and out of the city (very transient) and they practically GIVE things away - nice things. Brand new furniture, cars you name it. I sold my own car there right before I left to move back home and it sold within hours for asking - easiest sale ever. I made lots of money on there over the years too selling odds and ends. Also you can get next to brand new clothing, shoes and other goods at any number of resale shops in town - designer goods for a fraction of the price (Wasteland, Buffalo Exchange, Goodwill even!!). There is so much money in that town and young people who are fickle and spendy that they buy something, wear it for a few months and sell it for funds to keep up their fashion habit and keep up with the latest trends.
5. Don't keep up with the Jones's. Living in the city rubs off on you. You start to think things aren't expensive because you see them everywhere. Aston Martins, designer everything, gas, meals, rent, Urth Caffe runs, real estate, day trips to Catalina, or weekend benders to Vegas and the list is infinite. If you can stay focused and get used to seeing people throw around massive boat loads of cash and having fun all around you then good for you! (Hard to do in your twenties I will admit! 40's? maybe not so much?)
One thing I can guarantee is your cost of living will go up. It is a difficult transition to make coming from anywhere else because it is so vastly different than living anywhere else. It takes about a year at least to get your bearings with a neighborhood you like, a few normal friends and settling into a nice routine on things you like to do in the city (especially for cheap). BUT - I love LA and if you can move successfully it can be a very energizing, exciting place to live. Natural beauty all around you and good people if you look hard enough. I would probably visit a bunch of times and get the lay of the land before making the leap though.
I could go on but that's a start.....