Basement Conversion and Certificate of Occupancy? (hardwood floors, for sale, to rent)

[woodsart]

I'm looking at a house for sale that had a partial basement conversion (it originally had laundry downstairs; they moved it upstairs and then put in drywall, a closet, interior wall to make two rooms, and hardwood floors -- so it also has electrical and plumbing down there). The current owners don't know if the work was permitted, so I am guessing it was not.

1. I'd like to either finish the work or tear it out (if I had to) and finish the basement. It's huge and I could really use having another bedroom and office. I'd also like to add a bathroom down there and potentially a spiral staircase to the main floor (currently it only has a separate entrance).

2. For a year or two, if I finished it, I'd love to rent out the downstairs room/two rooms and bath to one person. I would not put in a kitchen as I understand you're not allowed to make two dwellings on a SFH zoned lot.

Questions:
- How hard is it to get a basement conversion permit? Would we have to rip out the floors and drywall and wall/closet that is there, in order to put them back in? I'd have a contractor. Is it difficult to get a permit to put in another bathroom?
- How bad are LA permit fees for, say, putting in a bath, wet bar, and a couple of walls?
- Is it hard or expensive to get a certificate of occupancy permit?
- If I inquire about getting a permit, will they force me to remove everything that was already done, even if I don't decide to move forward in doing any more work? I don't want to suddenly face a demo bill if the cost of doing the remodel properly is beyond me.

To be clear, I don't want to do the illegal stuff that is really common (i.e., unpermitted guest houses that are rented out). I am just curious about using the huge (like 700 square feet) space down there that already has windows and such in some way that is more productive than a storage unit. Even if I couldn't rent it out, I'd still like it finished so I have more usable space.

Thanks!