I don't know much about LPN programs, but as far as RN programs, I suggest you to find a school that is nationally accredited. You can find a list of schools by accessing National League for Nursing Accrediting Commission - NLNAC Homepage
The least expensive schools are the big universities and community colleges. However, most seem to have a waiting list for the nursing program. If you need to complete some or all of the pre-requisites, you'll be able to do that pretty much right away. But you will need to wait to finish your pre-requisites before you are even allowed to apply for the nursing program... and not only that... most have waiting lists of a year or longer.
A much faster way of completing the RN program is going through one of the private schools (refer to the NLNAC website are well), BUT ... be`warned... they ARE expensive! the trade of is that once you are accepted to those schools, you're in for the long haul. No need wait to apply for the nursing program. However, these programs are accelerated and very grueling. It is not recommended to have a job while you attend one of these schools, because classes go 100 miles per hour. It's no joke.
SO, it boils down to what you can commit to. As I said, private schools are very expensive, but they have the potential to put you in the field a lot quicker. The other ones take longer, but classesa re also longer... more time to digest the information.