Since you've stated your zone 8 I'm assuming your on the green side of Washington. That makes water issues less critical. Since you don't own the land and are still getting to know the owner, I wouldn't invest excessive money, work or dreams on this land (yet). It sounds like a fun
project though, and if understandings between the owner and yourself move forward, might be wonderful, even if it's 'guerilla'
permaculture and harvesting with the owners agreement. Look around the property and see if there are any erosion issues that need to be addressed as well as what the possibilities are for a dam or
pond. Dams and ponds are definitely something the owner needs to be brought in on (and probably pay for). One cheap possibility for erosion issues is bales of
straw slowing the water flow. Drive some good willow stakes through the bales into the ground. drive more willow stakes into the ground where you need things stabalized and slowed down. Most of the willow should
root and start stabilizing ground/slowing water. (Not the only solution, just a fairly cheap and easy one).
Try some
local natives like yampah or wapato. They should grow there easily in the right spot and are said to be good eating. (I view lots of
wild edibles on my property as my semi-secret emergency food supply as well as a normal supplement to my diet.
You might also try some plum, pear, apricot, cherry, persimmon and pawpaw seeds. Like the
apple trees, if they take off and you don't want that particular variety, they will provide established rootstock for grafting on a named variety you might like better. You probably already have plenty of scotch broom and alder on the property for nitrogen production. Bamboo will grow in that area if you can find a cheap source, but be careful of the running varieties.
I would plant tomatoes and an annual garden. The tomatoes, squash, peas and beans will self seed next year if you don't do anything more. Several bales of straw around them as mulch (I like around a foot of mulch, but I'm in a different area) should suppress weeds and not cost too much.
I would definitely introduce salmonberries, raspberries blueberries and huckleberries. I like blackberries, but I also like my hide intact so I prefer thornless varieties like triple crown (a good tasting variety). All of these should take off like a shot in your area. The little six packs for some of these can be fairly cheap and should do well.
Overall, I think I would start most of my seeds, (you might want to scarify some varities). Get them going at least a few inches high and then transplant them later in the year with some mulch (
cardboard under straw or woodchips to give them a fighting chance, woodchips last longer, but they are heavy in quantity if your nonmotorized) and place a marker so you can check on your trees occasionally. That way you'll get a better idea of what is working and what isn't and can adjust quicker than waiting a few years and saying "not many trees made it, guess it's time to try something different".
By all means try the seedballs. Treat them as an experiment and keep track of things you vary. Mark the areas so you can see what your success rate is. If it's successful, forget what I said about starting seeds. I would really love to hear you had an 80% success rate on the seed balls by doing X thing. It would mean less work for me (I'm looking at relocating in about 2 years and will need to start over on a new property).