I’ve never gone house shopping in Belgium but in the US at least, you would be fine just staying vague if they ask you any personal questions as long as you keep it friendly and aren’t rude about it. If you wanted to say you have an uncle or someone like that who is thinking of investing in apartments and he wanted you to check it out for him since you live in the area, that is a totally plausible story and will provide plenty of cover for you to be yourself. In my experience in the US at least, real estate agents want to show you the properties they are selling. They don’t want you to waste their time, but if they are selling a house they generally want as many people to check it out as possible. Ideally those are people who actually want to buy it, but anyone checking out a property they have for sale is always better than no one.