Buy a Cessna 150 and get an autogas STC. Fly the heck out of it for around $20 an hour. Skip the CFI route since it is difficult and unproductive as a part timer. In a few years you could have 1000 hrs and then buy a Piper Apache, get your multi in it and fly the heck out of it for around $40/hour till you get 200 hours. In my experience it would be cheaper and more fun than loosing your weekends as a CFI.

SkyHigh