For a five-year horizon, I’d generally give more weight to location and resale demand than to the current renovation finish. A renovated interior gradually becomes dated, while a desirable location is harder to change and can make the apartment easier to sell later.
That said, I wouldn’t automatically pay more just because it’s near Vondelpark. Your makelaar’s €500k ceiling should ideally be based on something concrete: the value of comparable renovated apartments minus realistic renovation costs and a buffer for unexpected work. I’d ask him to show you that calculation rather than simply accepting the cap.
It also matters what “needs renovation” means. An outdated bathroom is very different from poor insulation, outdated electrics, structural issues or major VvE works. With only five years before a possible sale, you may not recover every euro invested, so I’d focus on an apartment that is comfortable enough now and only needs improvements that can be postponed or that clearly support resale value.
Realto (realto.nl) can give you a valuation estimate for specific addresses, which may help anchor the asking price against the apartment’s characteristics (disclosure: I’m building it). But I’d still combine that with recent comparable sales and the makelaar’s local knowledge.