You will need to dig a footing or be on an existing concrete slab. In the north (assuming your in the USA) the footing needs to extend below the frost line, which I'm told is 3 feet.
Cinder block is required for the first few feet (2 or 3 courses) of wall height to prevent water damage from rain or snow.
Anything that will change the outside appearance of the home will most certainly need a builders permit.
If this is your first project, you're going to need some help. There's a lot of skill sets required to do this.
Are you going to drywall the interior or leave the studs exposed? What about the exterior? Vinal siding? Stucco? etc... Any electrical in these walls? Windows?
There are kits available that'll make it easier, but at that rate, you may as well just have them install it.
I've wanted to do this to my house since I've moved in. Our porch is covered and on a concrete slab. I haven't decided yet if I want to use the space as a office or a first floor bathroom / laundry room. I put the expense around 7k to raise the floor to the same height as the house, drywall inside, playwood and vinal siding for the outside, and I'll reuse some of the windows and doors from the part of the house its attached to.
Nothing you can't do by yourself with another hand. Score some books from the local home store and plan it out. If you get stuck, make sure you know who to call.