I know NHF loans are available through banks, who charge a lot in interest but I am not an expert.
If anyone works for a credible Mortgage provider in Nigeria, please tell us about your service on this site targeted at Nigerians who live abroad and don't have a clue.
http://www.business-travel-nigeria.com/home-mortgages-in-nigeria.html. Use the form found towards the bottom of that page. This is free advertising.
If I can't verify your address then I won't include your details. Thanks.