Single-speed vs Multi-speed bike purchase I am looking at buying my first bike as an adult.  I grew up in a neighborhood that was very hilly, so am used to getting bikes with gears to be able to do hills more easily.  I now live somewhere comparatively flat (long shallow hills; E.g. 0.5 mile at a few degree incline, &lt;5 degrees), but am very out of shape.

Question:  What are the real things I need to consider to decide

1) Whether I need a multi-speed bike at all

2) How many speed bike I need?

For completeness &amp; context
I am about 6' and 160 lbs but not in shape at all.  I currently walk or bus pretty much everywhere.  I'm looking to use the bike mostly for getting to/from work, not necessarily to get in shape.   My ride to work can be 0.5-3 miles, depending on if I decide to ride to transit or bike the whole way.
Single speed bikes tend to be very low end bikes--aside from fixies, but those are a different animal altogether.  As such, you almost certainly will want a multispeed bike.  Don't get too focused on having a specific number of gears.  Instead, focus on a bike that meets your needs.  For commuting, you'll mainly be looking at commuter bikes and road bikes, and you'll likely be looking at a derailer bike with at least 16 gears.

Visit some local bike shops with absolutely ZERO intention of buying something that day.  Depending upon where you live, the selection of shops may range from great to sparse.  Get a feel for the place and how they treat you.  The customer experience will range from great to awful.

I strongly urge that you stay away from big box stores and only shop at local bike shops.  You will have a far better selection of bikes at a local bike shop, and service is non-existent at big box stores.

What's available at bike shops in your area may be completely different from what's available in my area.  As such, it's impossible for anyone on the Internet to make specific recommendations.  It's best if you look at the inventory of bikes in shops in your area.  Something that you have to custom order or drive 100 miles to pick up adds a lot of unnecessary expense and hassle.