You can now pick up 88-93 E-series sedans for between $8K - $16K depending on condition...so that frees up some dollars for modifications...or repairs. If you find an accident-free car, you should be pleasantly surprised at the supreme quality of the paint and interior, which has withstood years of weather-related abuse.
By now, most of these cars have reached over 100K miles, so you will now be dealing with replacing components that will have age-related failures...radiator, head gasket, timing chain, suspension bushings, and some A/C and electrical components.
Fortunately, they are some of the best made cars, and probably the most common in that era of MBs history. So there is a world of knowledge with respect to expert advice and guidance on troubleshooting problems and going about repairs. The other nice thing is that parts for these cars are relatively inexpensive, even for OEM. Many of the repairs are DIY, if you are so inclined.
MB cars are robust, and you can enjoy many miles of service with proper maintenance. MB service at the dealerships are hugely (and sometimes unecessarily) expensive when doing non-warranty work, so find a trusted mechanic that will do good MB work for less.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car