I don't have access to whey powder. What's the next best alternative food-wise for building muscle?
According to most points of basic research the main type of protein that your body absorbs in a manner that you'd want is eggs. One of the best absorbed proteins by the body. Can be made to taste almost however you'd need it to with spicing, and is really relatively inexpensive. You could go with fish, tuna is your best friend, again cheap but straight from the can 26 grams at about 50 cents a can. Can't get better than that if you're aiming for about 200 or so grams a day. The go to in food again is chicken. Not as good with the protein/fat ratio as tuna, but if you're not worrying about that then you can make it taste way better than the past two.
If you're thinking shakes or things of the sort, you could go about getting into an egg based isolate powder. There are vegan protein powders as well, look into ALOHA plant based powder.
There are a ridiculous amount of things out there with a high protein content. If there's really no health reason behind not wanting to take in a whey protein then you shouldn't avoid it. You can get a relatively good powder in Dymatize that will yield about 80+ servings for about 60 bucks from BB.com if expense would be a reason for not taking it something along the ways of this would be good.
Assuming you are in search of protein-packed foods, let me remind you of your best friend. Fish. An average serving of any type of fish usually will easily provide anywhere from 20-60 grams of protein. Fish is usually somewhat affordable for a middle/working class citizen; at about $6 or $7 a Ib. Heck, if you're up for it or have money problems, you might even want to catch your own fish. But the point is, fish is your friend, and eating it will build strong muscles.
If you search over the internet for sources of protein, you will get a bunch of results and foods that you can choose from. Even with whey powder, you need to watch your diet as it is healthier to get your protein directly from the food you eat and rely less on the supplements.
If you are a vegetarian, load up on beans and nuts. Best practice would be to eat eggs right after your exercise.
The wording of your question suggests that whey would be the best protein source, which might be questioned. Whey is cheap (since it is a by-product) and easy to isolate.
Egg protein - others stated - is good, since it has the optimal combination of amino acids, but the yield ratio is quite bad, since one egg has only about 6g of protein. I'd see beans and nuts rather ambivalent because of the high abount of starch and fat respectively. I'm no low-carb or low-fat bigot, but satisfying your demand of protein (especially when you want to build up muscle mass) with beans or nuts would mean, that you'd increase your carb- or fat-intake respectively severly. Good alternatives (besides lean meat - which I will not discuss, for I have not experience with because of my vegetarianism) are (low-fat) curd or cottage cheese. They are not too expensive but contain a quite good amount of casein, which is digested way slower than whey protein, BCAAs (at least curd afaik) and vitamin B12.
And you can easily make shakes out of curd. Just put it in a shaker with some milk, water, etc.; add some vanilla or cinnamon and shake it.