Which envelope for paying vacation home owner in cash?
 

I'll be staying overnight in a funaya (boat house) later this year and payment is in cash. I'm not 100% sure if there will be a check-in counter/money tray as the home is rented as an entire unit and check-in is done on-site. The owner is Japanese.

Can I put the cash in a white US mailing envelope and gaijin smash the confusing envelope rituals while still respecting the "cash is dirty" norm? If there is a tray, I can take the cash out & place it in the tray and tuck the receipt back into the envelope. Or is there a specific envelope which would be appropriate for payment, not a gift? Asking ahead of time in case I'll need to plan in advance to find the correct envelope. As you might guess, there isn't a combini for miles.

If you're staying at this place as a customer, I really don't think you need to care too much about those details.
There are different kinds of special envelopes for money when giving cash to someone as gift or token of appreciation in situations such as wedding, family get-together (eg, otoshidama or money gift to your nieces), etc.
In your case, I think you can hand the money in any envelope... usually money is transferred in envelope that opens along the shorter side (unlike US envelopes which open along the longer side). Unless this boathouse is a really fancy place, you could probably even just hand over the cash as is.

Thanks! Yup, just a customer, and not a fancy place. It is along the coast of Kyoto prefecture so erring on the side of politeness :) I think I can find a bank type envelope at PaperSource.

Any plain envelope will distinguish you as a person of great refinement. Hand it over with the phrase "Dozo. Kakunin shite kudasai." ("Please check it"). Even a sheet of letter paper folded around the notes and taped down is good. It is, after all, a transaction - not a gift.

If making a lodging payment in cash then it is a business transaction, not gratuity. In such case it is totally acceptable to give cash as is, do not have to be in an envelope.

Putting cash in an envelope is done at weddings, funerals, even otoshidama (お年玉) at New Years. Those are from old time ritual where when giving money to express your thoughts, gratitude, greeverance... The bottom line old thought is when receiving money for emotional related situation is like world's oldest profession, hence hide money in envelope.

But your situation it is simple business cash transactions. No different from paying cash at konbini, no different from paying cash at a hotel, no different from paying cash at a restaurant.

If you want to use an envelope then plain white envelope is recommended, I will not use brown envelope. But keep in mind, it is a business transaction so it is standard to confirm in front of you that proper amount was received from you. If you give in an envelope then there is Japanese thing about not opening gift in front of you. When receiving money in an envelope at wedding, funeral, otoshidama, then not to open the envelope in from of a person to check how much inside. Giving money in envelope for your stay will make the person receiving little uncomfortable to open in front of you to confirm proper amount was received.

If giving cash at the end of the stay as a gratitude then make sure to use an envelope.

Thanks for the detailed explanation. I'll pay by handing over the unwrapped cash politely, then, as the whole purpose of asking is to avoid making the receiver uncomfortable.

I'm not the elegant type (especially by Japanese standards). I do try to pay some attention to such details to avoid reinforcing negative stereotypes.