Hello!
The difficulty in responding to a post like yours is that they tend to reveal more than was originally intended. You leave a lot of things out, not just your identity. For one thing, though I can understand your concern for your friend, I cannot help but wonder why you feel compelled to speak for her, assuming that she is an adult and can speak for herself. After all, you are talking about a young woman who has been in a relationship with a man for three years and presumably has not sought the aid of others to help rescue her; you are taking it upon yourself this errand without figuring out the possible ramifications of interfering in someone else's life, no matter how well-intentioned. You say that you want her to get a grip on life but what do you perceive is a proper "grip?" That is a vague notion, one that is entirely subjective. Let us try to understand one thing and this is important; your friend--let's humanize her further and call her Jane--is enmeshed within a life--that you have deemed inappropriate--by her own volition; if she really wanted out, she would embark upon an escape if you will without the desire of well-meaning friends to go into rescue mode. She's a grownup; she doesn't need rescuing from any outside source. Rather, what she needs is to see how untenable her situation is or may become and thus determine to rescue herself.
Another disturbing level to which your post descends is your concern for the apparent age difference in Jane's relationship with her partner. Yes, she may be 22 to his 40 but he is the man with whom she chose to cohabitate; if she doesn't spend sleepless nights worrying about the 18-year difference in their ages, why are you? An abusive relationship respects no age gap; a 22-year-old guy can be just as abusive as a 40-year-old man. And what do you mean by "abusive," anyway? You did not go into detail as to what Jane's lover does to her that would warrant being tagged as abusive. Her penchant to remain indoors, rather than to seek a more active life outside of the home, certainly suggests that her partner is to some degree controlling--not uncommon with older men who are in a relationship with much younger women. However, controlling is not exactly abusive unless you have witnessed specific acts that would place the situational dot over the "I." My response to you is not to doubt you in any respect; what I am doing here is to point out that prejudging a situation into which you are not directly involved does not necessarily make it as you call it.
When women find themselves in an abusive relationship--particularly one that involves both verbal and physical assaults--the women are reluctant to leave. Why? Because there is always the hope, often misguided, that they will somehow change the guy--that he will wake up one day and realize the error of his ways and do right from that point forward. That almost never happens and usually the woman has to reach rock bottom before she finds the inner strength to leave on her own. Although you have described what may possibly be a controlling relationship, you have not really described an abusive one. For example, you said, "she never leaves the house until she has to work..." In an abusive relationship, the male partner would not allow his woman--I say "his" because they tend to treat their partners as property--to go outside to seek work; their fragile egos rest on exercising total control, which means that the guy must remain the sole breadwinner and caretaker, lest she go out and meets someone who will actually love her for who she is. Jane will seek work when she feels that she must, as you say; that suggests to me that Jane is not so much abused as she is guilty of making the wrong choices in men. She seems to prefer men who are older because they are most likely to take charge, sort of like a father figure; she also seeks them for the security they offer, more so than a man near her age. Unfortunately, she also appears to have an affinity for men who are not particularly ambitious, which is why they both are struggling. It may mean that the money he manages to make--when he is working--either is never enough or he is spending it in things or activities that have little to do with keeping their house solvent. You report that they have had three evictions so far; where is the money going? You're getting involved in a situation that is more complicated than Jane is letting on, at least to you, and instead of rallying strangers at this site to your side to advise you on how to carry on your notion of a rescue, it may be more instructive to step back a bit and figure out what the true story is without evoking the prejudgment that can only muddle--or should I say, muddy--things even more.
You should talk to her as a friend, hang out more, and find out if she is happy. If she is, let her be; if not, try to help her out. You are a very nice friend doing this for someone.