I would not have risked starting the engine on 20 year old belts that could have been the end
a proper belt job with a new water pump will be around 2k, if it’s been standing for a very long time I would get the head gasket done at the same time this will possibly push the bill to 4-5k
i say these things as I have had to do exactly the same, along with new bouncy bits and fuel pipes and all sorts of other things
its taken me the best part of 5 years to do all this and I have spent 5k GBP, 7k$ with no labour charges
keep in your mind that there is no such thing as a cheap Porsche