There are a wide variety of items that can be bought in individual packs (usually 6-8) that cost about $0.25 - $0.40 each. Every time I go to the grocery store I try to buy one such item, usually a $2.50-4.00 expenditure. After a while this turns into a large volume of breakfast foods or snacks. I try to only buy items that will last forever without going bad, or perishable items that I would eat myself.
Most guests will only use a few of the items (or none at all), so your cost per guest could be as low as $0.50 or as high as $3-4.00. If they are booking for 3 nights that at least $150 for me, so it’s a very small percentage. Only one time did someone really go nuts and drink 12 Kcups and eat a ton of snacks, but it was a recurring guest who paid me over $800 in one month. I would have her back any time, food notwithstanding.
Juice boxes (no need to refrigerate)
V8 in cans
Dried fruit / nuts / granola
Boxes of raisins
Granola type bars - huge variety here, healthy and not-so-much
Hostess coffee cakes or Little Debbie cakes
Those square snack crackers that come with peanut butter or fake cheese filling
Keebler products such as cookies or crackers
Instant Oatmeal or Grits
Small boxes of Kellogg cereals, variety pack
Coffee, tea, sugar, creamer - the first time you buy it will be a few bucks, but you restock at different times. The sugar packs have lasted months and are no place close to running out.
Perishable - yogurt, milk in boxes, OJ, frozen burritos, breakfast sausage sandwiches. I used to put out fruit but now I only do so if requested.
I know this really sounds like a lot but I bought it all over time and each guest wants something different, so I could probably go another 6 months without restocking the dry goods. Most of my guests are about $1.00 a day.
My local store has an aisle with bulk goods and often has sales on these items so I stock up when possible.