First, learn all you can about the pluses/minuses of the organ systems of these cars as they are 40+ years old and will suffer from vehicular geriatrics to varying extent.
I am somewhat new to w113 cars, my previous experience with 50-60s Aston Martins and Alfa Romeos. But for that price point ($30k range), you should be able to get an excellent, but not perfectly, "restored" 280SL/250SL/or 230SL, with the 280SL being at about 10%-20% higher premium (for reasons that don't make sense to many 230SL owners, but are supported by the general market).
Excellent, *original* (meaning not restored, and not needing it, other than tires replaced along with some mechanical consumables) vehicles are much rarer and will fetch much higher price points, usually to go to the rare original owner. Not matter how beautiful the repaint is, no matter how beautiful that restored interior and rechromed brightwork is, and matter how many hundred grand was spent on the restore -- the original, unrestored and unmolested vehicle is more valuable and rarer. You should be able to get a beautiful w113 that is *restored* in your price range with the proper search, like the SL website or another members car. Beware of eBay, especially at this price point. Do not except complete original parts, however -- many of us here do not as we enjoy bringing good cars back and driving them, taking advantage of the abundant OEM/Mercedes parts available.
The price point also is entering the realm of a quite decently kept 190SL as well.
1967 230SL (Manual, rustless driver)
