I would think that things have changed dramatically since the Cartier building was purchased i.e. prices have risen 60% (or whatever was needed to generate the wonderful profit). In judging whether now is a good time to buy in you would want to look at the expected return on what you are buying into, and the costs and charges you will incur in doing that. You would do the same if you were buying a house - if you are thinking of buying into a large building in Paris then you probably need to do a lot more homework.
As for expected return, a yield of 4% seems low to me given you can get generally get more about that without incurring any costs or risk (e.g. deposit accounts).
As for costs, you should get detail on all of those. The first costs will be those incurred in buying the building. These probably come to about 20% of the amount you invest. So you are down 20% from day one.
The second set of costs will be the interest payable on the loans taken out to buy the building. With the ECB rate at 4%, then it's unlikely they are paying interest of less than 5%. I would certainly question borrowing at 5% to invest in something that only yields 4%.
The third set of costs are the charges. It is given as 0.7% of gross value. This probably means BOI are taking a charge of about 3% per annum from the amount you invest.
So, that's 20% down day one. You then are paying 3% in charges each year. You are investing in something that yields 4% but you are paying interest costs of 5%. What's missing? Well really all you are hoping for is a lot of capital appreciation to make up for all those costs&charges. Whether that will happen is anyone's guess. I would say something like this is high risk. Not for me!
If word in your work is definitely to buy this, then I would assess who is giving out that word and if they are also buying into it. If, on the other hand, they will only benefit if you buy it then it's difficult to take that as independent advice no more than you would trust any salesman telling you it's a great opportunity. But looking for independent advice is the right road to start off on.