There are many reasons why a tight and close knit family unit can be beneficial to the development of its younger generations. The closer a family the better the supporting structure for a young kids needs. It might be quite difficult to support a child so you will need all the help you can get, however it is very common in modern day society for women to be in the work force, while leaves the need for someone to care for the kids while they are at work.
Granny can serve as a nanny, you wont need background checks, the price will be much cheaper, if not free and the child will get valuable time with their grandparent.
However you must remember a few things to ask before allowing granny to be your nanny.
It is still a stressful and tiring job looking after kids, especially in your older years. It may be rewarding but do not put too much strain on granny.
Granny wont be on call as she has her own life too. Whether its going to bingo or meeting her friends for coffee, realise that she has a life as well.
Have some rules for what granny is allowed to do and how restrictive she should be with the children. She shouldn't contradict what you have already laid down as ground rules.
If you want to or feel you need to, the discuss a basic pay rate for granny.
Hope this will help foster a wonderful granny/grandchild relationship. Check out this awesome I Love Grandma kids t-shirt.