Split by bedroom.
And if she stays half of the time or less, she pays half of that bedroom cost. Give her a deadline, like half way to date to the vacation day.
Does she seem like one of those that takes advantage of others, is she usually fair?
Also depends on if you get along with her or not and what has she helped you with in the past. Yes, there are some that take and take and never give.

If that is the case for my sister, I would require her to pay the price of the bedroom. She's like that, a taker and not a giver and very indecisive and full of complaints. So, I learn to not give her any additional options or open discussion because it would just drag on and on for months. And of course, she was very inconsiderate and took very late showers-like midnight! what the h---!

Anonymous wrote:I would use this way of splitting (by shares) http://mathforgrownups.com/beach-week-splitting-the-costs-for-a-week-at-the-shore/

I think that approach works well when there are multiple kids sharing bedrooms, etc. in this case I’d could the child as a full person however, since they are getting their own room. OP, I don’t blame you, it gets easier when they are a bit older.

One year, when my sister came without her husband, we calculated a per-person rate. Kids and adults each counted as a person. Another time, my step-mother wasn't there for all of the nights. That time we did a per-person, per-night rate. And yes, they can both be difficult and we needed to make them feel like the costs were fair.

In reality, my uncle ended up buying most of the food, and refused to be compensated for it, so the rest of us therefore made out like bandits.

Boy did my family rip me off. It was divided by family. I was single so paid the same as my siblings w spouses and kids. Not only that I didn’t get my own room. I had to bunk in the kids room!

I would use this way of splitting (by shares) http://mathforgrownups.com/beach-week-splitting-the-costs-for-a-week-at-the-shore/

Anonymous wrote:OP you sound like a princess. Just share a room with your kid and make it cheaper for everyone! People do it all the time.

She's paying for the 5th room so how does it get more expensive for everyone else?

OP you sound like a princess. Just share a room with your kid and make it cheaper for everyone! People do it all the time.

OP, I often rent houses with big groups of friends and am in charge of dividing up the costs. Some have kids, some don't, some are single.

I split the rental cost by adult. That way single people don't have to pay twice as much as people in couples, and people with more kids don't have to pay extra for a room that crowded up with kids. The food we divide up by person except small kids count as 1/2 a person since they eat less (and babies who don't eat don't count, obvs.)

However, this is assuming that each family only takes up one bedroom. Since you insisted on two bedrooms for your family, you should pay more.

Given all these considerations I would suggest something like splitting the rental costs per adult except you and your DH count as 3 or 4 adults to account for the extra bedroom.

If your sister's boyfriend comes for a couple of days then you could just do it by bedroom, or do a more complicated equation involving the # of days each person is there. I usually charge people for rental costs for the whole trip even if they are only there for part of it b/c it's not like we could have gotten a smaller house or rented it out to someone else for the days they chose not to come.

Anonymous wrote:How much more was a 5br house vs a 4br? Just curious because you insisted on the 5br and that might have driven up the cost for everyone.

OP here- it’s a few hundred more but by paying for the 5th bedroom we more than make up the difference.

Thanks all- I’m going to suggest per bedroom. She definitely has the money, that isnt the issue.

Anonymous wrote:

Anonymous wrote:If the $$ won't matter to you, and it will to her, then just for the sake of being a kind person - you pay the extra.

Huh? So OP is supposed to pay for the 2BRs for her 3-person family plus a share of her sister’s BR? That’s silly.

PP said if the money is not a big deal then she should cover. We supliment for my in laws all of the time, to get them to come. They can afford it, but they are cheap.

How much more was a 5br house vs a 4br? Just curious because you insisted on the 5br and that might have driven up the cost for everyone.

Anonymous wrote:Per bedroom because you generally have to rent based on the bedrooms needed. Now if she offers to share a room with your child, then you pay for 1 1/2 bedrooms & she pays for 1/2.

The fact that the boyfriend may come for a few days means this won't work.

If OP's sister wants the benefit of her own bedroom (including the ability to have her boyfriend come for a few days if he can), she has to pay for it. After all, if you rework it based on people rather than bedrooms and then her boyfriend does show up for a few days, do you rework it again based on people? And does he count as a full person or just half (since he won't have been there the whole time)? Similarly, does OP's child get counted as a half person because he's smaller, or as two people because his toys might end up taking up more common floor space than an adult person's book would?

You need to differentiate between what's fair and what you want. What's fair is to split the cost by bedroom. However, if you really want to include your sister, cost is a big issue for her and others are prepared to pick up a bit of extra cost, then by all means charge her less. Maybe she gets allocated the smallest or least desirable bedroom. Perhaps you could say you are happy to pick up some extra cost but would she mind babysitting one evening so you and your spouse can have an evening out. You should probably be clear that this applies if she is on her own If her boyfriend does come for a few days then they really should be paying by bedroom.

Anonymous wrote:If your DH didn't come, would you expect to pay less?

I think splitting per bedroom is the fairest way by far. If she doesn't want a bedroom (ie: will sleep on a couch or on the floor somewhere else) that's one thing. But everyone would need to agree with that too because I would not like someone on the couch during my beach vacation.

I think these types of trips only work out when people can go with the flow, everyone is willing to pitch in and is willing to trust no one is taking advantage. If there's penny pinching and bean counting, this trip won't be fun. Dishes, cooking, shopping, lugging beach shit can all get really old if everyone isn't helping.

Ugh, yes. Lost friends this way. It's a nightmare. Hopefully things will be better for you, OP, especially because this is your family. You sound incredibly considerate.

Per bedroom because you generally have to rent based on the bedrooms needed. Now if she offers to share a room with your child, then you pay for 1 1/2 bedrooms & she pays for 1/2.