There are a lot of places that you could base yourself at, live cheaply, and take your time working though your courses. Thailand is a great option, IMO, because you can get a huge variety of diving just a hop and skip away by basing yourself here. You do a couple of courses, go diving someplace wonderful to gain experience, do another course, go someplace else to dive some more, etc. From the island I live on, you can easily reach dive destinations not only in Thailand, but also Malaysia, Indonesia, the Philippines, and Maldives. These places represent some of the most outstanding and varied diving in the world, and this is why I've settled here. Of all the countries of SE Asia, I find Thailand the most welcoming, easiest to adjust to, and culturally most fascinating. Yes, I'm biased, but I chose this place after a lot of thought and research!
BTW, one of my students who did something similar to what you want, but started out as an Open Water diver, was a policeman retired on disability after a horrible accident in the line of duty. I think his disability payments, which continue throughout his working life, made this a viable option because when added to the earnings of a dive professional, there was plenty of money for him to live comfortably. Those who are cautioning you to use the funds to train for a career with a better earnings potential are pointing out an important consideration.
BTW, one of my students who did something similar to what you want, but started out as an Open Water diver, was a policeman retired on disability after a horrible accident in the line of duty. I think his disability payments, which continue throughout his working life, made this a viable option because when added to the earnings of a dive professional, there was plenty of money for him to live comfortably. Those who are cautioning you to use the funds to train for a career with a better earnings potential are pointing out an important consideration.