I am an aspiring model in Hawaii.  Buying clothes here is not very cheap.  I would like to go to local shops or botiques to ask about wearing some of their clothes for photoshoots.  I just don' know how to go about aproaching them or if they will take me serious.  How should I go about this.  Thanks in advance

Ask. The worst they can say is "no".

take along your portfolio to show them that you are legit.

in all honesty, they are probably going to say "no." they won't gain anything from it, unless you can promise to get the photos published.
what you should do is approach small, local designers and ask them directly. offer to wear their clothes to big events and carry their business cards with you....they probably still won't just loan you the clothes or give them to you for free, but they are likely to cut you a good deal....

If you offer shots, make sure you have the consent of the photographer. After all, it's his/her work (copyright) that will be the over-riding consideration.