I did this for a few years when I was on a corporate verizon account (read: no throttling, edit: and unlimited data). There are a few ways you can setup ddwrt/tomato/etc to connect to your phone's hotspot when it is present and serve it to a home network. I started out with just one router doing the connection and rebroadcasting as my own home SSID, but I had stability issues, so I would recommend what I moved to, which would be a router acting as a wireless client and router for the home network, and then adding an access point to that for rebroadcasting as a home only wireless network as you don't want all your devices connecting directly to your phone wireless hotspot. It was very stable after moving to a setup like that.
Then you can use one of the phone apps, like tasker or macrodroid, and have it set to turn on your hotspot on in the presence of your home and then off when you leave.
Overall it worked very well and saved a bit each month, the performance was not as consistent as cable, but when it was good it was faster than the connection I have now. You could also sell this on the idea that your place is more secure when you leave as it is disconnected from the larger scale outside world (anyone local could still get in through the apartment wireless..), but that has its downsides as well (no remote file hosting, remote home automation, etc..). But it served me well for many years, so I would say it is a viable option if you have a plan that does not have caps or throttling.
