Congratulations, Joan54!  It's quite a compliment when a professional company sees your work and wants you to come work for them.  This just recently happened to me, so I know your dilemma.

Firstly, you must ask the director if his company has any costume agreements with other companies.  If so, then send your actors measurements and show specifics (Twelfth Night) to the costume designer of the companies and ask if they have anything that will work.  Don't specify colors or patterns, however.  If they have anything, they will let you know and tell you when you can come take a look (give them at least a week).  You go and HOPEFULLY someone has pulled them, however, usually you're pointed in the general direction.  If you're lucky you'll find just what you need, but YOU have to do the running to the various theatres.  If you borrow from another company you MUST return the pieces exactly as you received them ... no alterations, just tacking things us.  Personally, I think that takes much more time than sewing from scratch.  If you have your own stuff, even better!!!

I don't think it's unprofessional to sew backstage, personally.  I used to do it all the time.  You have the person there for a fitting when they can break away from a rehearsal.  I'd check with the director first, though.  If he says yes, then pack up your machines (I'm assuming a standard machine and a serger?!) and head off to the city.  Be sure to bring everything you'll need ... I keep all my notions in a large fishing box; fabrics in a large clear storage box.  Some companies maintain a costume shop and a resident hall, a place where the resident designers (costume, set, lighting, directors, etc.) can stay if they need to be in town for an extended period, or if it's too dangerous to drive (snow storm, exhaustion, etc.).  You might ask about that, too.

You failed to mention family?  If you're married, how does your spouse feel about the whole thing?  Can you afford to take three weeks away from your children?

Financially, can you afford to take time off from your job?  Do you have sick leave you could take?  As far as the theatre is concerned, have they shared the specifics of the budget with you?  Will you get paid or simply have a budget?  You need to nail all this down before you sew stitch one.

I was offered a nice little sum PLUS a budget for sewing/renting stuff.  I took a day and weighed my options and decided against doing it.  I simply had too much on my plate.  I'm not sorry I didn't take the job, it just wasn't the right time for me.  However, if it's something you really want and can give up everything else for the next three weeks, then go for it!!!

I costume for a high school play

When I have rented costumes from a local university they charged me $26.00 per item (if a matching suit that would constitute one piece) They needed to be cleaned before returning however and any alterations needed to be removed.   We signed a form that listed the costumes in detail with any current flaws noted.

Thanks for the support...I took the job. I couldn't help myself...I am so star-struck.  It was so great to be treated like a professional!  Assistants met me at my car, carried the costumes in, helped me load later.  I am so used to doing everything myself I felt absolutely pampered.  I got almost the entire cast fitted with costumes I have already made so what I have to do this week is some size adjustments, a couple of new hats and some extra shirts.....not as much new sewing as I expected.  I'm not entirely thrilled with the money they are paying me but I know I negotiated poorly because I wanted to do it so badly I would have done it for free and that probably showed in my body language.  On the other hand I was assured that there is more work with this theater and I can hold out for more in the future.

Anyways...thanks again for the advice and support...got to go...lots to do...

How did it all go, Joan?  You sounded so excited about the entire experience ... now we want to celebrate with you!