Fair bid for a used car?

There's absolutely no way to answer your question(s). You haven't given any details, except the asking price and the fact that you're looking at some type of Porsche.

 

I think that is a fair starting bid. I suspect the dealer will try to split the difference with you and only come down $2k - $3k in price from $50k. Most dealers need to make 10% to 15% on their inventory. So on a $50k car, they may have $42 to $45k in it for their costs.

It really depends on what a similar car sells for elsewhere. You can check cars.com, eBay motors, craigslist, and hemmings for other people selling similar cars (both dealers and private party). Most dealer's asking prices are going to be on the high side. So, if you find several similar cars for a range of $43k - $52k, then the dealer has priced the car right. But, if you find most much lower, then maybe the dealer is being very aggressive. And, if you find several a bit higher in price, then it would make me wonder what is wrong with the $50k one at the dealer; is it a salvage title?, does it have a hidden problem?, is there damage that isn't shown in the pictures of it?, etc.

If you cannot come and see the car yourself, make sure you pay to have a local mechanic do a detailed PPI (pre-purchase inspection) for you. Do this BEFORE you buy it, not after.

IMHO, I like to find cars sold by broker/enthusiasts who sell just a few cars a year on their websites. Typically these cars are in very good shape, not on the open market, and are being sold from one hobbyist to another. Often these cars are being sold at a fair or good price - especially when their condition and rarity are factored into the deal. An example of this broker/enthusiast here in Virginia, USA, is Dave Olimpi's website. He is an FCA concours judge and very well connected to Ferrari and Porsche hobbyist clubs. Take a look at his website and you'll see the kind of cars he occassionally posts there for sale. I visit his website about once a month just to see what new interesting car he has to offer.
http://www.daveolimpiautomobiles.com/ (click on the "cars for sale" link on the top).

 

i can get it for you for 10 dollars, however, the price of my services run at $49,990,
seriously though, i agree that without more information, it will be tough to answer your question thoroughly. i don't know exactly how the exchange rate will affect the price, shipping, etc. good luck though!