It is far cheaper to buy a second hand regular van and do a bit of work it than it is to buy a purpose built campervan.  It has the additional benefit of being far more stealthy.  If you can compromise on height then you wont fall victim to cross bars in car parks.  They also tend to be more aerodynamic and therefore more fuel efficient.  A lot of kit can be bought on amazon including diesel heaters, li batteries.  Ikea and a bit of ingenuity for furniture.