Get married. Have a baby. Change your mind. "I'm sorry, honey, but my heart is calling me to law school. We'll get a private bank loan to cover the living expenses for the next few years, and then we'll be just fine when I get out, cool?" What's she going to do? Walk away from you as a single mom? Why? Because you want to get more education and will eventually be better off financially? No. She'll stay. You'll have it all.
I also don't think that a deception as you've prescribed in your last paragraph is ethical, no offense.