It can be a fun weekend car. For maintenance, do regular maintenance (change the fluids, spark plugs, air filter). You may also need to clean the carburetor. 

I am not a Mercedes Benz fan, but those are pretty good cars. That said, I would use it as a weekend toy since its 23 years old and it would not make sense to daily drive it. Just take good care of it and it can be a decent car.

An old thread, but worth chipping into for readers also considering a Mercedes 190e variant.
These were built when Mercedes were synonymous with quality. They were MASSIVELY over-engineered at the time and with regular servicing will run for decades.  You know a car is good when they're commonly used as taxis.
Parts are still plentiful and fairly cheap, with plenty of good quality pattern parts available as alternatives over OEM parts.  Often genuine MB parts are surprisingly reasonable.  They are a doddle to service DIY - even the later 1993 models, as they are still of the era when mechanicals were accessible rather than hidden under plastic covers.
My tip is to get a base model, preferably with as few of the electrical options as possible (great in the day, but a bother to source now).  The only electrical option I have on mine is the passenger side mirror - because it wasn't an option.  Try and get one without a CAT for simplicity
Take the trouble to inspect it rather than just buy on eBay.  I bought a rust free example with near immaculate trim and exterior, just under 100,000 miles on the clock, running sweetly with just a few niggling running trivial repairs to do, for £2,500 (a snip over $3,000). I'd avoid going much over that unless it's a real beaut.
And DO use them as daily drivers - the engines on them were meant to be used and want it..