What business can I start with 600k.... please your candid advice is needed. Thanks

It depends on what you can really do as a business, my advice is to look around in your area and see if there is anything new you can introduce there,another thing i am suggesting is that you should look into internet business check on the numerous business models on internet and choose one first before looking for a good mentor on it that is already making a living from it who will take you by the hand and teach you everything you need to succeed in it.