My friend is looking at purchasing a Dell 2in1 laptop. His hopes are that he could possibly dual boot windows 8.1 and Ubuntu so that he could have a windows and Ubuntu 2in1 experience. What I mean is that he could open windows and have windows tablet and laptop. And then log into Ubuntu and switch from tablet mode to laptop, so basically a 4in1! Is this possible? If so how would you go about doing it?
Yes, this is definitely possible and it can be done just the same as installing Ubuntu on any other system.
This answer will provide you with all you need for setting up Ubuntu on a Windows 8 system.
Note: It would be a good idea to give your model name a quick search - something like this
<model_name> with linux, which will bring up any problems users have had once having installed Ubuntu, since it seems that some 2in1s have problems with Ubuntu not supporting particular hardware features.
Use the Desktop version of Ubuntu, not the tablet version, even though the laptop does have a touchscreen.