- Your ISP is [ISPs are, to your 2nd point] actively hostile to running "servers" from your connection, so you must either pay a ridiculous premium for that privilege, or jump through hoops to evade their intentional breakage.
- Your other cousin does something illegal (sells drugs, posts revenge porn, threatens a public official) using your host and now the police are knocking down your door in the middle of the night and dragging you in for questioning. Even if you avoid charges, your neighbors eye you suspiciously from then on.
- Your ISP is [ISPs are, to your 2nd point] actively hostile to running "servers" from your connection, so you must either pay a ridiculous premium for that privilege, or jump through hoops to evade their intentional breakage.
- Your other cousin does something illegal (sells drugs, posts revenge porn, threatens a public official) using your host and now the police are knocking down your door in the middle of the night and dragging you in for questioning. Even if you avoid charges, your neighbors eye you suspiciously from then on.