All of the options above are good ones. There are many. All have strengths and a few weaknesses (or a few things you can live without).
You can get yourself a large external hardrive and just create folders for jobs. Store all of your job data there. You can create folders within folders for easier management.
Another option is on-line storage. You can get a ton of storage now for just a few dollars per month from a number of very good sources: Microsoft, Google, Zoho, Host Daddy and many others. The biggest thing you need is storage. Lots of it.
Just think it through. Once you start storing files, you will be amazed at how quickly they build up. You will not want to move them from one vendor to another often and the vendors know that. For years we hosted our own data. Now, the server is older, the software is no longer supported, etc, etc. We have chosen to use an off-site storage facility. They run the server, they provide the IT, and the increase in bandwidth is phenominal. We do use SSL, and some additional site security measures.
If we had to provide a new server and software it would cost us a minimum of 15K, and it would begin to age the minute we drive it off the lot. For just a few dollars/month, we get unlimited storage, increased bandwidth and new software every time we turn on our PC's not to mention access from anywhere we have wifi, 24 x 7. I calculated that with our monthy cost per employee, it would take several years to pay out 15K. Then we would be stuck with another old server and software. It was easy math.
As for the files you are talking about, records of installs, drawings, notes, all of that is stored permanently in a folder per site/per client. We use a simple interface to store and retrieve the records for now. A simple file storage webpage(s) will do until you decide how you want to manage it. There are a great many options available to you for that too, and they will only get better.