This is certainly not a complete list but here are a few things that are very important in regards to sustainability:
The biggest need will always be money. Don’t kid yourself; you are going to need a lot of it -especially as your orphanage grows in size. Foreign or domestic support can help in this regard but it is a good idea to look at sustaining your project through other areas. Running a Primary School or Kindergarten is a great example and one that has worked well for our organization.
As the children increase, you will find that you/your family are not able to “do it alone” and you will need help. Good people are hard to find, especially when you need them to work for cheap! Start looking for help long before you need it.
A good website that clearly states your goals/purposes. This really does make a difference. These days everyone uses the net, you’re using it right now! It is important to get your name out there as this can help with both of the above points.