Here's the info I gathered on Tanzania. It seems that most companies need to be contacted to find out the requirements, and maybe they'll be more informative then the ones in other African countries.
ZanAir: I don't know about requirements. Get in touch with them for the piston hours. The Let's still need a type rating and this is in the range of 11000 Euros. (www.zanair.com)
Tropical: They are overhauling the entire fleet, and eventually will need pilots. A good place for low time guys to start off in and work up. As for requirments you need to get hold of them. (www.tropicalair.co.tz)
Flightlink: They have C206, Seneca II/III, Islander BN2B-20 and C208B. Based in Dar-Es-Salaam. (flightlinkaircharters.com)
Sky Aviation: Several twins. They operate C402B/C an Aztec and a Cherokee 6. A relativly new company. Nothing of their requirments or working conditions. (unfortunately no link)
AuricAir: They have everything from little singles to big twins (Caravan, Seneca and L410). (www.auricair.com)
Coastal Aviation: One of the biggest operators out there. Safety is cool. The pilots are experienced, and entry requirments are high. 400+ for a 206 and 2000+ for a Van. Flying to some pretty out of the way places and some very rough strips.
Comment from a Coastal pilot: It does take a certain character to make it in Coastal, it's not for everybody. It's hard to get onto the Van since most pilots are upgraded internally. But if you want to come and fly out in East Africa for a while with a descent Company and fly serious hours. Then I'd say look up Coastal. It is very hard for the new guys, but managment wants dedicated people who give that little extra for the job. It's not just good enough to just fly you got to help out in all factions of the company from time to time. Often your in some middle of nowhere place or in another country where you have no support staff. It's hard work, but I've had a fun doing it. You'll work hard but fly all over the country and it's neighbours. (www.coastal.cc)
Kili Air: ran over them while looking for Tanzania flying pictures (the ones posted here are from their site), a company incorporated in Tanzania and is based in the town of Moshi on the foothills of Mt. Kilimanjaro. They have flights in Tanzania and Kenya. Flying C404, C210. May be worth a check. As I work as a designer for me a nice website tells me a lot about the company and Kili has a really nice one. Small, well positioned and has a well defined image. They are my personal favourites (like MackAir is in Maun – www.mackair.co.bw – or Pleasure Flights & Safaris, based in Swakopmund – www.pleasureflights.com.na). (www.kiliair.com)