Full time is the way to do it. Save up the money and then go for it.
But as others have stated, don’t pay up front. Make sure you sit them down and tell them exactly what you want and the time you have.
I was assured mine would be completed in 3-4 weeks, through no fault of my own I finally got the rating after 6 weeks. Basically they were too laid back and not used to 3rd party work, and naturally the aircraft went in for its 100 hrly. Training was to a good standard though.