Should I use an LOI or an Option agreement

[Karl Smith]

I'm looking to wholesale 2 - 6 unit Chicago properties. The owner wants to sell them together. Both properties are C class, vacant and need full rehabs inside about $15-20k per door; kitchen, bath some wall replaced, replace some stolen copper pipes plumbing etc. We decided that we were not going to rehab these buildings but would like to wholesale them to an investor. I would like to know if I should use a LOI or an Option agreement to get control?

Thanks
Karl S.