Running a classic car is not the same as having a modern car with a fixed length service interval and a standard list of items to check and replace every few thousand miles. You could approach it like that and you would find the cost is pretty cheap for the the parts: filters, plugs, points, brake pads, fluid changes etc. However you will probably find that a lot more work becomes apparent as you start to use and work on the car. Bits will break off, some parts outside of the regular service interval will be up for complete replacement - hopefully not something that is made of unobtanium. Perhaps you will start to wonder if you should upgrade the suspension or fit a nice stainless steel exhaust system. Then it can start to get expensive.
I have kept a log of everything I have ever spent on my 1968 Spider (except petrol). In the 18 months I have owned it, I will have just about spent as much again as the purchase price. I was fortunate not to have any major body work to attend to but I did do some expensive stuff like upgrade the suspension and fit a new soft top - if you can curb your enthusiasm in this area then you won't be too far out of pocket.
But that is me doing all the fitting myself. I can't imagine how much it would have cost me to pay a garage to do the same amount of work - probably as much again as the parts.
That may sound like a horror story and I don't want to put you off. I purchased my Spider with a pretty good idea of the work involved and made my offer accordingly and kept a contingency fund. A cheap fixer-up may seem like a bargain but it will eat into your money, always buy the best example you can afford. As to the car in the advert I like that it was originally a California car - you hopefully don't have bad rust problems but I'm wary of the RHD conversion.
Good luck
