First concern is not STD but 'first meeting protocol'. Be very careful meeting someone you meet on the internet. You certainly should not be scening with him at this stage. A public meet in pub/cafe/restaurant, with friends of yours either nearby or on the end of a phone is your first step. During this meet you can discuss limits and negotiate what you want to do with each other. At this point, when you are still 'two men meeting in a pub' rather than 'Master and sub', is the time to mention basic safety and what you will and won't do to each other. My advice, if he says no to a condom then you walk. You may also want to consider dental dams. You could also at this point ask him for evidence of recent negative HIV tests and hepatitis vaccinations (and make sure you can provide this yourself).

Remember, you are not his sub until you agree to be his sub and even then you are not legally obliged to do anything he says...