Start by going to your local comic book shop. Many local comic book stores have artists come in regularly for signing and sketches. A lot of employees might also moonlight as illustrators. They may not be Manga but they might be able to do it or know someone that does.
If you already have an artist in mind, drop them an email or twitter. Say you want to discussion commissioning them for a new comic you're funding. Be sure to include words like commission, funding, paid, etc... So they look at it. Otherwise you're just another guy trying to get a free piece of artwork to them.
You might also need to hire more than one artist. A lot of times one person draws, another inks, and a third does just the lettering.
Again talk to some guys at the local comic book shop. Tell them what you're looking at doing and what type of hourly rate they would charge for it. Take their business card and stay in touch with them. You're going to need fans and distribution at some point anyways.
As far as costs. This is really dependent but some factors to consider:
B/W or Color Ink, Paper Quality, Page Count, Size of Run. Depending on size of run you'll need a lawyer to speak to and make sure there's not going to be issues on that side. And finally marketing / sales / distribution.
Like DA01 said this all depends on if you're doing an actual print run or just putting it up online. Either way though if you don't promote it online or in stores then nobody will know it exists. Especially if you're paying money for it you'll want to try and generate some revenue back.
As with any new business you should expect to lose money on the first few issues. Once you get a distribution and reader base it will be easier to get your costs down, and potentially sell a page or two off for advertising.