If people are super motivated to learn English, they'll usually say yes to homework. Follow through with this an assign some! If they're too busy, then don't expect it. Often, an English school might be a good source of referrals and it doesn't hurt to ask. Or, a school with a lot of international students may be a good place to start in our experience. Remember, as an ESL teacher, you can't read minds. If in doubt, ask the students what they want and they'll tell you!