Unless you are looking for an ultra-basic car with an almost trouble-free engine coupled with rock-bottom running costs (and overlooking its poor brakes), do not go for the Maruti 800.
You will start feeling 'fed up' of its spartan interiors, in no time.
Further it can be seen in used-car ads, that most second-hand Maruti 800s are over-priced. There are better options at those prices.
After all it is a 20+ year old Suzuki Alto [CA72(?)] made by using low quality Indian components to make it the world's cheapest car (in 2005).
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Hope you will find the following links (written in an Indian context, however) useful.
This link is about buying a used Maruti 800, and they recommend going for the 12-Valve, 5-speed model that came in 2001.
http://www.indiacar.com/buyusedtips/800_t_...n07%2Findex.htm
This article shows the truth about the "crystal light" model launched in 2005. (Maruti Suzuki has reverted to 6-Valve, 4-speed.)
http://www.indiacar.com/roadtest/roadtest_...une05/index.htm