When socialists say they want to collectivize private property, they use a meaning of private property which equates to “means of production”, or “capital”. The goal is that there won’t be owners of capital earning money simply by employing other people to work the capital and stealing a part of what they produce (surplus value).

In your example, summer cottages and family farms aren’t means of production, so there’s no reason to redistribute them. Pensions and retirement were guaranteed to everyone even in the USSR, where women retired at 55 and men at 60, so I can guarantee socialists want you to have a pension. Small businesses that employ other employees would have to be collectivized eventually, which could mean that the owner simply becomes one normal worker in the business, working alongside the previous employees instead of above them. Regarding the apartment, you don’t need to rent out an apartment if the rent of your apartment costs 3-5% of your income (as was the case in the Soviet Union). Land ownership and inheritance are a bit grey. Obviously nobody wants to collectivize your nana’s wedding dress, or your dad’s funko pop collection. Obviously we would want to collectivize if you inherit a big factory, or 20 flats that your mom rented out. For things in the middle, it becomes a bit more grey, so there’s no easy answer. I bet everyone would agree that uprooting people isn’t generally a good thing.