Start with the easy stuff, buy a can of flea powder that is safe for cats and dogs. The powder is a pain to use so dirt cheap. Dump it all over the floor in her house. If you google “how to make a flea trap” you will get tons of hits, again dirt cheap fixes and they work. Those 2 measures will really help take care of the fleas in the house.
Now for the animals, only the cats and dogs will get the fleas. Any soap will kill fleas especially cheap pink shampoo or dishwashing detergent. Soap all the animals thickly, and I mean thickly, pen them up in a room and let them sit in the lather for at least 15 to 20 minutes, then rinse well and spray them with a mixture of water and cheap PINK conditioner. Not too much of that though, that can give them the runs if they ingest too much. This will take care of the fleas on the animals. You have to do it periodically though, there is no 1 fix cureall.
The heartworms will kill the dog eventually. If you know a farmer, ask him for a small bottle of ivermectin, that is what they use to dip cattle and sheep. It is not licensed for parasite control on dogs but it does not hurt them. I have been using it as a parasite preventative and heart worm is a parasite for years. It will not cure heart worms but will keep them from getting worse. If she doesn’t know a farmer tell her to go to a livestock feed store and beg them to open a jug and sell her a small bottle, dose at 1mg per 10k of body weight. Just put it on the dogs back between the shoulder blades. Some can be given orally, we put on bread and disguise it with anchovy paste, but it depends on what kind you get.
Those are my best suggestions, won’t cost that much and can be done at home by you and your friend.