B2L2

DIY is easy if all you need is a small rectangle screen.  Doing a large size one, you want the stronger frame.  HomeDepot has the standard size screen door pre-made too.

I had some company to made our screens (door and windows) since I need a door in the screen for open/close the windows.  I don't like to take out the screen everything to open/close my windows.  My patio door is over-size and the HomeDepot one doesn't fit.

Almost all company who works on screen door do free estimation.  But I could tell you they have a big price range from store to store.  Better ask first.