Above all, before you want to be a resident of Madagascar, think carefully if this country suits you because behind the postcard life is different from what you can imagine, I invite you to read my article on this topic.
To go to the concrete, you can not directly apply for an investor visa and if you are a tourist visa in Madagascar you are obliged to leave the territory to obtain it. You have to go through a visa called "transformable"(This is not the tourist visa) which has a validity of one month that you must order at the embassy of Madagascar of your country, for the list of embassies, this way.
For the list of documents to provide, I invite you to directly look at the Embassy website of Madagascar.
Worker / investor visa
Here you are in Madagascar for a month, now you have to act fast. I'm sure you were told that it takes more than 6 months for the papers to do, not to mention the badchiches and back and forth in the offices so you've talked about hiring someone to do it in your place who will get there quickly thanks to this knowledge.
Attention, I'm not saying that these people are not good, I did the same thing at the beginning but there is much faster AND LEGAL, I discovered them during my last request (2013) and they told me renew my visa in less than 10 days (ok it's a renewal not a first request but still), I went to ask for the list of documents to provide (available on their website), I have 2 days to prepare (lists of models to print here) and they called me 8 days later to recover. No round trip, no envelope under the table and everything in order! (You can not imagine the head I made, I did not believe it ^ ^) I speak well on theEDBMThey have an office in Tana and also one in Nosy Be, I have never been to Nosy Be so I do not know if they are as responsive, feel free to share your feedback in the comments.