I agree with 5-7 100%. Do you research first. Decide what kind of build you want to do, meaning frame mount, rack mount, friction drive etc. If you don't know what those terms mean, you'll find out by doing your homework here on the forum. They all have their pros and cons. You also need to research you local state laws. Motorized bikes are totally prohibited in a few states so I understand. Engine size is governed by states as well. Some states limit engine size to 35cc, but I think most have a max of 50cc. I will recommend that you get the largest engine allowed by law in your home state. Japanese name brand engines are probably your best bet too, be it a 2 or 4 stroke engine. All Jap engines are not made in Japan though. Most are. I have a Honda that is manufactured in Taiwan. But as long as it has a Japanese name on it, you'll be all right with it. There are a lot of choices out there. Most builds/kits are fairly simple, especially if you're mechanically inclined. Don't let the info you start gathering scare you. You can get a descent kit (engine, mount, total complete kit) for under $300.00. Do you research and what you don't understand, start asking here on the forum. There are a lot of good, friendly experienced people here.