Anybody have experience turning single-family into duplex

[Richard Flake]

My father-in-law approached me and my wife about turning his current sfr in Metairie, LA into a duplex via ~$100k add-on project. His lot is zoned for it and he says it will easily rent for $850. We would be funding the construction project but I have a lot of questions about legal ownership of the property as well as how a loan for a portion of the project might work. Has anyone done anything like this successfully? Thanks!