Why does no one discuss Rent Collection Loss Percent ?

[Amit Patel]

I am getting into the game and having a hard time getting data form even some exp. investors on this.

The vacancy in my area is roughly 5% (urban NJ areas).
However, I use 10% for all my calcs for 4-family homes..
Now, for the life of me, no one (even when I get to a very specific neighborhood) can give me good info on what % losses from rent collections I should use/assume is the amount of rent I won't collect due to having to evict, non-payment,etc. I'm assuming that like vacancy, there must be a general number people use for A,B,C, and D properties. I understand it will change from neighborhood to neighborhood and on what kind of tenants you have but I really want to factor this in somehow.