When researching garden apartments and condos in Chicago, much of the anecdotal information on the Internet is very general and negative. Much of this information is from people with no construction knowledge or empirical data. They may have had a bad rental experience or ownership experience, but this can be said for all properties. However, just as in any other dwelling garden apartments and condos are subject to quality of construction, one's budget and one's preferences. The most prevalent reasons to own a garden unit is location and price. You can simply get a better location withing your budget and a 30%-50% discount to comparable condos on the first floor.
The main objections to garden level homes (usually 50% below grade level) are; Fear of flooding from exterior or back-ups, lighting, security, and humidity/temperature control.
Here's an easy read addressing construction features that address humidity and temperature in basement living spaces:
Many basement condo conversions have good sump pump systems, drain tile to prevent seepage, properly insulated walls and or other flood preventing features. Many of these units have had years of comfortable living... so just be diligent.
My own experience deals with several clients owning garden condo units and "duplex-down" homes with the lower floor living space is 50% or less below grade. Most, including my-self, have had positive experiences. I've owned a duplex home for three years and we have several systems in place to keep our lower level dry and extremely comfortable. Some have experienced some type of flooding or back-up issue and had to correct the problem. In each one of those cases I know of, it had to do with proper plumbing maintenance of the building and the cost varied greatly. That is, if you are thinking of living in a garden unit you should inspect the common plumbing situation of the building.
This garden unit below in Ravenswood is wide, highly upgraded and has industrial plumbing improvements to prevent back-ups.
If you are looking to buy a garden level condo I suggest interviewing qualified inspectors who can enumerate the important points they will check. I also recommend having a licensed plumber come out and run a camera check/system check of the situation. This can cost up to $500.00 plus the physical inspection ($200-$500 depending on the size, complexity of the home). However, if you can get a terrific unit with all he features you want in the location you want... for 30%-50% less, a proper inspection will be worth it. Some buildings will already have excellent plumbing improvements work and records.
As for safety, I personally have no evidence suggesting garden units are a higher break-in risk than houses, other apartments and finished lower levels of homes and duplex-down condos. It's true you may not be able to leave windows open at all times like a top floor unit. But this is all part of the pros, cons and pricing. As we speak, I sit writing in my lower level with the windows open. We have a security system and close them when we leave or at night.
Lighting will depend on size of windows and interior light fixtures. "Canned" or recessed lighting is my suggestion for finished basement levels. There are plenty of above grade units that get little light due to surrounding buildings, however they may be worth the price and location for many people.