…and why not to do it.
That is probably a little bit extreme, especially if we are just talking about a little raised platform off your back door. These can be a great summer project or something to keep occupied with during stay at home orders. One of the primary issues encountered during a home inspection though is work which has been completed improperly and/or without permits. Much of this type of work can be corrected with relatively simple repairs but decks and stairs are the number one cause of injury in and around a home. There is a lot of engineering that goes into the design of a deck or attached balcony to help account for the numerous ways which they can fail.
A good way to complete this safely as a DIY project is to do it as an “owner builder”. You do not need to be a licensed contractor to do work on your own home in some cases and can still have your design and work reviewed by city engineers. In my experience, they are (mostly) helpful and just want to see things done properly and safely. Plans can be purchased online or can be drawn by an individual, although that could be a daunting task for the diy’er. An excellent source to review proper deck construction is DCA-6. A link to this guide is here (.pdf warning).