Guy with 5 million flyer miles

Guy doesnt have a house,  he just flys around on cheap flights to rack up miles,  he has a lot of rewards cards,  and does other things to get his miles.  He is a bit extreme but I didnt know you could do this.

The last time I had a lot of miles was when I built my house and charged all my materials.  I didnt pay for acticket for years.  I also heard of guys charging travlers che ks then returning the che ks but keeping the miles.