1,  If dad has more money, it is only natural he spends some on his kids.  If you had more money, would you spend more on your kids, I am guessing you would.

2.  Waking you up -- if SD goes to the bathroom, will that wake you up?   If DH asked her to be in by 1, would she still wake you up if she walked around.  If kid not in any trouble (drugs, etc), staying out till 2 on weekends is not the issue.

3.  In many cultures, parents let older kids drink at home.  His call. 

Sounds right to me. She's just had a year of doing what she pleases, why should she now have restrictions?  As long as she's as quiet as possible coming in, and not getting trashed at your home, I'd be OK with those rules. 

(I personally think the 21 drinking age is ridiculous.  Canada has the right idea with 19).

I'm not 100% sure what country you live in. If that's below the legal drinking age I'd be concerned with legal issues coming up later, particularly when the kid tries the "well dad said I could!"  But that's just my concern.

As for the restrictions. I think if she's staying there this summer, she should have rules to follow. Your house=your rules. If her coming home so late is causing issues, your DH can ask her to arrive earlier.  She's not a kid, so I wouldn't say a curfew. Just a time when you need everyone home for the night. If she has a huge issue, moving out is ALWAYS an option. That's why when a lot of people move out at 18, they stay out. They like the independence associated with being on their own. 

If the waking up isn't a huge issue though, I wouldn't sweat it. It sounds like she's only there a few months before she goes back.

At 19, my parents had more guidelines for me than rules. I didn't have a curfew, but I had to be as quiet as possible when I came in later than 9pm (which was many nights, not because I was out partying, but because I worked until 11pm or so). My bedroom was the guest room. My car got parked on the street. I could drink at home but no one else could come over and drink with me. I didn't have to pay rent over the summer, but I did have to pick up groceries if the house needed them.

There is a middle ground between treating a young adult home from college like a "full adult" and a child. A young adult shouldn't be held to the same rules they had when they were a teenager in high school, but they should realize that they are being gifted with free housing, which comes with responsibility to those in the home.

My parents gave me a curfew when I came home from college the first winter break. I laughed - um, I get mostly A's in college with no curfew there, didn't party, was responsible....so WHY now?  They didn't have a good reason and I never lived at home again.

I say your rules your house with concessions for good behavior.  Is she a good kid, getting good grades, responsible?  Well, maybe no curfew on weekends and an earlier time home during the week (because of work day schedule for others in the house). So long as she maintains respect for others schedules that would be fine, but if not, revoked and back to a specific time home.

She should have chores and things to do around the house.  Is she working?  A part time job should be found! 

As for the drinking, is it heavy drinking or just light/moderate?  If she's doing it to get drunk, underage, not allowed.  However, I am a fan of teaching younger people to drink moderately and within reason.  Waiting to the arbitrary age of 21 seems insane to me and invites mis-use.

and do what she wants.  Paid her own bills. Even an adult living in someone else home for free, have rules to follow 

When your underage Skid drinks at home... call the police. Just because daddy says it is okay does not make it legal.

So... play the get the authorities envolved card.

Daddy may learn something and hopefully so will the Skid.

As far as the "I'm and adult" thing.  The response is... adults don't live with daddy. If SS is an adult, SS needs to GTFO and find his own place to live... completely on his dime.