Unity 4.3 free work with oculus

Does not, because unity free won't let you use external dlls. There's a workaround available, but I didn't tried it myself, I think I read it costs a good chunk of performance.

Your other option is Unreal Engine for ~20$ monthly or just once (and then no further updates).

If you want to go Unity you need to get a Pro license, but you can experiment for a month with a trial (that won't allow for commercial releases though).
UE4 is cheaper to start with, but aside from the $20 per month (and you better plan for a regular payments since you want the updates for the Rift - at least for the near future) you will have to give them a split of your earnings as soon as you reach a certain threshold.
If I were you, I'd make the engine decision based on what you plan in the future (just demos or commercial work) and the content you need. Unity has a great assetstore that allows for a lot of time saving purchases (codes, shaders ...) and access to a broad selection of models, animations and sfx/music. I would love to try UE4, but I am already too deep in with Unity on the purchased assets side. Stuff like Polyworld is just too great for VR to switch.

I am in Unity's camp for now, I know the system well and work with it. I was going to get an oculus for a bday treat and start developing for it. Mostly demos maybe for commercial someday, and to have a cool new toy. Now it seems though that since I don't have pro unity or plan to get it, then means sorta useless buying the dev version. Bummer