i will highly recommend you stay with one main site that refer to "local office" and you can also do many different maps on the sub domains.

I working on 2 sites that are the same for what you referring ( not franchise but with local offices) and they are up with all main keywords and city sub domains sample at 123locksmith.com

also as you said it will be way more easy for you to control this site and rank it up.

hope that help

HI, first i will support other answers and will not recommend the redirect from the same reasons.

regard the URL i will like you to look at this site that i am working on www.123locksmith.com and see the way we did the city pages.

working great with this system and this site is up in major keywords and city, i will recommend you have some changes in the content and not just change the city name.

i will recommend to start with the city pages from day one because if you will work on a strong DA by the time you get to this pages it will be easy to work on.

hope that help you

Mike

That's and interesting question and to be honest i didn't pay attantion to this one before as an SEO factor.

So i did some research and look to me that there is no effect of your SEO plan or your site ranking if your domain renew every year or every 3 years.

Infect i manage more then 3000 domains for myself and my customers , most 1 year and all ranking very high t so  bottom line after research and from personal experiance i don't see any problem or different with one year domain

hope that help

Mike