I had one that just appeared in my hell strip when I lived in Orange County. I left it in bush form, but then a nearby sweet gum started to ail. The city forester had to come out to inspect the tree and sign off on its removal. While he was there, he saw the six year-old oak, whipped out his pruning shears and limbed it up into a single trunk tree. It looked quite a bit better

I have its descendant growing on my back slope now, but this one decided to be a single trunk tree from the beginning.

as with all pruning.. if you have a goal.. its easy to decide how to accomplish it ... the tree is currently in its natural state ... and that is fine for the tree

the hard part.. is predicting whether that goal will change a decade or 2 down the line ...

its hard to tell ... from the first pic.. when it might start infringing on the sidewalk and road ... and at that point ... something will have to be done .. and it might be hard to accomplish such ... by that time ... [and its usually a problem.. when some utility comes along.. and massacres it]

whereas ... if you start now ... you may be able to guide its future growth .... to avoid potential future problems ...

i hope that makes sense ... its a bit early ... ken

If you have room for an eventual 30-35 ft. wide crown, why not just leave it?

We had many Live Oaks out in foothills. I agree with Ken that to start the proper shaping will make life easier in the future. Proper pruning lightens-the-load and helps eliminate branch die-off and limb loss in the future. You'll have a beautiful tree if it is done correctly.... now and in the future.