Loans are mostly because I sometimes inadvertently pay too much downpayment and get into negative. Or to secure downpayment. Of course with high rates.
About tenants, yea maybe they could call sometimes. Although you would have to avoid it getting spammy once a player has too many tenants. Maybe there could be events about for example handy tenant fixing something, or neighbours complaining about loud ones.
It would also help if there was more transparency about what tenants traits lead to, some are obvious but I am not sure if smoker or loud affect prices for example. Or whether its better to have a messy tenant or one with a dog.
Yea thats fair, developing plots can come later. Another layer that I thought is missing is taxation, I imagine there is a fair bit of tax on rental income in Germany. And it could be made interesting by having to factor in depreciation, maintenance etc.