Jaka,
I understand your passion to buy a 280SL ... and reason for your need to buy one at a relatively low price ... <USD 20k. However, there are several decisions that should or will most probably influence your interest in a given car besides the price... how much rust damage, etc.
Some questions, for example:
Does it matter if the car's been in an accident and it now has unmatched numbers?
If the engine's not "running" but everything else is reasonably sound, does that matter?
As you are clearly aware already, in general, the lower the price the more issues with the car .... and the converse... in general, the better the condition of the car the higher it's price.
What this means is that a drivable, street restoration car is going to cost you more than you're willing to pay at present. This therefore means that purchases of parts you'll need for restoration or just usability will force expenditures beyond the price you pay for the car.
If there's body damage/rust, upholstery, chrome pieces or pieces that require rechroming, instruments that don't function, etc. all will cost labor and parts.
Which brings me to the next issue and questions you need to consider carefully before you plunk out $15k or so for your passion.
Do you have a spare garage where you can take the car apart as necessary or a place where this can be done without forcing you to move the car for extended periods?
Do you have tools and a place where some of the disassembly and / or repairs can be done by yourself or with help of a friend?
Do you have any experience with mechanical aspects of cars and engines? and other mechanics on a car?
No matter how you cut it some things you'll have to pay for out of pocket ---- and a likely total cost to get the car to a reasonably reliable driver without spending a cent on paint or interior upholstary, etc. is in the range of $5k - $8k. Add any body/paint/chrome work and you're adding another $5k - $8k minimum. (in Yugoslavia). If you need genuine replacement parts, add more.
So assuming the lower estimates, you'll be adding upwards of at the minimum USD 10k to a purchase price --- not to mention tranport from US to Yugoslavia. The more issues with the car (say one for $12k) the more you'll be spending later. No matter how you cut it, you'll be spending at least $25k (US) for a driver with some degree of reliability... and the more you bring the car back to it's original condition or close to it, the closer the total price will approach $35k - $40k.
So, is your issue with low price one of cash flow... i.e. you only have $x to spend NOW... but will have $y later (whether to spend on purchase or to spend on restoration)? Are you able and with space & tools to do a lot of the labor effort (dis-assembly, assembly, engine mechanical work) yourself or are you forced to farm it out to vendors in your area?
Here, for example is a 280SL from a reputable California MB restorer/dealer who takes cars on consignment or buys them, fixes them up to a given degree, then offers them for sale, as well as offers space on his website for other sellers to advertise their cars. There's one now on his site for $15k... but it has several deficiencies which is why the price is $15k.... it's a driver though.
It's in your price range, but with deficiencies (honest MB classic car dealers will bring out all the issues related to mechanical, cosmetic, and restoration issues. In particular, this one as no hardtop available, and numbers don't match... among some other things that limit the ultimate restored value of this car. I bring it to your attention only to discover what issues you are willing to pay for or not pay for in a 280SL?
http://www.oursl.com/listing-forms/inventory.htmhttp://www.oursl.com/listings.php?op=showads&modelid=7http://www.oursl.com/listing-forms/listings-det.php?op=showdet&aid=2431 
