Most citrus trees are grafted. Is that lower branch sprouting from above or below the graft union at the base of the trunk? You should be able yo see the graft scar. If the limb is coming from below the graft, then it's root stock and will not produce tasty fruit. If it's coming from above the graft, then it will be good fruit, but the tree will probably always be very lopsided and deformed.

In addition to checking to see if the new branch is above or below the graft, you may want to see if you're in an area getting hit hard with HLB. That may be why the previous owner gave up on the tree - not that it had HLB, but that he thought it was inevitable. https://californiacitrusthreat.org/

https://www.cdfa.ca.gov/plant/PE/InteriorExclusion/hlb_quarantine.html