I just got a new to me Old Town predator 13 on Friday, what have others doing to rig these out? I have already put a Lowrance on it but I don't know what else will make it better than it already is

Take it out several times and see where you naturally lay equipment or reach for things.
Paddle keeper? Anchor cleat or anchor trolley?

Anchor trolley system, a good anchor line setup, rod holder (if it doesn't already have one), and a milk crate for tackle and rod storage.

^Solid Advice

I moved my crate over from my other kayak, I am thinking about the anchor trolley as it doesn't have anywhere to tie off to

I have a Predator 13 and the first thing I found I needed was a rudder. I also installed a anchor trolley but I have since installed a second anchor trolley on the other side.

For the anchor trolley I use either a 3 pound anchor, drag chain anchor or drift sock depending on conditions.

I also need some ideas on how to store 6 kayaks. I don't like how they take up so much room in my barn, I need some kind of rack for them

Google "kayak rack" or look on Pinterest, you'll get a lot of ideas. I built a rack out of PVC pipe so I could stack my two kayaks and not lose so much space in my shed.

You have 6 kayaks but are wondering how to rig the Predator?

I know it sounds crazy, but my in-laws keep four of them at my house in the barn. Two of them are mine and I don't want to drill holes into the nicest kayak I have owned that aren't needed. Also I have been out of the kayaking game for a few years and don't know a lot about all the accessories. When I first looked at the predator I saw all of the scotty mounts in the hatch lid and was wondering what everyone puts in them all

Charge them a storage fee or make them buy the material to hang/store the kayaks. Browse around the YakAttack and Austin Canoe & Kayak web sites, you'll find a lot of accessories.