ESL teacher considering a contract in Lagos

Hi! I teach English (ESL) and have been offered a contract with a French family in Lagos. I have lived in several countries, but Nigeria is by far the most "adventurous" destination I have considered. My contract includes use of one of two duplexes available to the family and participation in Shell's health insurance scheme. Safety is obviously a concern, but there are several threads which address this issue.

All of the threads I have read, however, are written by people who work for, or are married to people who work for, large internations. As an employee of a private family, I must consider how much of the security provisions would be available to me. Also, as an employee of the family, how can I be covered by the health scheme?

Of vital importance is the question of a work visa. If I am employed by an expat family, do I need a work permit, and what are the requirements? My first overseas teaching position was in Lisbon, and before I arrived I asked about getting a work visa. The school where I was taking my CELTA course assured me that it would be no problem. In fact, it was a big problem, resulting in my working "freelance" for three years with no possibility of getting a work visa, and therefore, no contract. I don't want to go through that again.
Another issue I need to consider is finances. While the most costly expense, housing is covered, I would like to find a resource for information on cost of living expenses. Banking is also a concern. In a country which is known as a center for scams, how does one deal with money issues? Assuming that setting up a bank account is no problem(I try not to assume too much, but...), can one safely use an ATM card for purchases, or is cash the rule? Is cash safer than an ATM or credit card?

Finally, I'm not the typical ESL teacher. I'm not twenty-something and just out of school. So, what is life like in the off hours in Lagos? Are there places where the Protected content "hangs out?" Restaurants and pubs? And after dinner and a pint, how safe is the trip home?

Thank you for any advice you can offer. I realize I have covered a lot of territory, but my experience has taught me that now is the time to ask these question; I'd like to avoid stepping on a "landmine" and then asking"-Hey, what was that click?"