Karmadhi

instead of the ptz (the price for the ptz is high) get fixed cameras and cover the angles you need. ptz sounds fancy but it's not very practically. also I would suggest hd-cvi, basically hd-cvi and hd-sdi are the same things, HD over coax. my personal opinion is that the hdcvi quality is better, but that's personal. you can go for a tribid dvr, which means you can cover some areas with IP cameras, other with hd-cvi and/or analog. I've worked only with dahua tribid actually and it's very reliable. the other brands should be ok too. for tribid I've only tested out dahua. the price is acceptable too.

you need to open: tcp and rtsp ports too

open guest accounts for your tenants. in this way they can check the cameras but cannot change the configurations.

purple is better, it's gonna last longer and it's more reliable. green is gonna get burned soon. let me tell you why: green is made for computers and computers need a lot of bandwidth. so green is made to handle that huge traffic going back and forth. now the dvr/nvr uses low bandwidth. using a green hdd means the hard drive is gonna spin uselessly handling a low bandwidth. that's gonna consume the hdd and it's gonna fail soon. on the other hand purple is made to handle dvr's low bandwidth and doesn't need to work/spin uselessly. a normal computer hdd is gonna fail in 1-2 years (most of them, there are exceptions of course). till now a purple hdd never failed on me. also another recommendation: if you wanna use a normal hdd for your surveillance go for the seagate ones, they are more reliable then wd green (from my experience).

he can change the password and p2p is not gonna work on the installer's phone

you have to change the IP do you gataway format