as a first car and if its your only car I would suggest not to make such a venture unless you have spare time and cash at hand for the initial ownerhsip phase to fix it, have at least 4 lac spare cash if you wanna make it a reliable daily driver.
Firstly when looking at the car go for one that has service history and service record and stay away from ones where owners say just been doing oil changes and its perfect.
then see which engine you are going for either m111 or m271, the m271 is most common as m111 was only till 2002, that engine (m271) you wanna get as low milage as possible as the timing chains give out as early as 100,000 to 160,000 km if oil changes are not kept up and even then the cam gears can still wear and thats a very expensive fix. on the m271 engine look for leaking cam magnets in the front, if its been leaking since long the oil wicks the harness for the o2 sensor and also the ECU which is bad news, 7 out of 10 cars I see the intake pipe Is held on with tape so check that, try to experaince it in a cold start parked at owners home rather than after its been warmed up, observe for leaks observe that all the unders shields are intact they are usually missing, most likely youll need a complete suspension re do if owner hasnt done by this age to really get the feel how a mercedes shoudl drive like, pay special attention to steering rack too, make sure you get two keys as replacement keys are xpensive, if there is any sort of warnign like SRS or check engine etc and owner says oh its a simple sensor or just minor thing then walk away as if it was so minor he would have rectified by now, you would most likely have to change all fluids if previous owner hasnt and thats a 50-70k expensive on its own, also get a good option one there are some really reallty basic w203s wiht little options that arent really worth getting but focus on maintenance history as preliminary reference
also make sure AC works no funny noises from dashboard etc, theres a lot of risk however its worthy of invesrment if you wanna keep it for a long time (I have mine for 6 years and counting) and itll give you far far more pleasure however initial period youll have to put in the money and the time to make it right and then enjoy it year to come, there will never be such a thing as just buy and drive an old Mercedes in PK unless it has miracoloius service histroy using genuine parts.
I would tread super carefully and think twice if you arent prepared for it.
