We are working on a medium sized multifamily and a single family flip, so it's a good mix to learn.

One of the standard setup is to have each property in its own single member LLC in the state of the property.The property LLCs are then owned by a holding LLC in WY or NV to benefit from their good charging order protection.In addition, you would use a C corp as management corporation to take salary (if needed to show steady income for future loan approval), retierement, medical and other fringe benefit.

My family is outgrowing the unit we currently live in and we would like a single family home while holding onto the two family.

What types of properties (single family, small multi-family, mobile homes, condos, etc)?

Regarding single family and multi units, you can grab a total rehab or you can grab one already rehabbed and ready to rent.

I am pre-approved for 4mn USD for a single loan...but have questions.

All in all you just spent 18 months+ on a single note.This is how I started, using only our own money.

It sounds like your single family is very tight as you focused on getting into the place and having your expenses almost paid. 

I am looking to purchase a single family property worth approx 160k.

Hunting for single and multifamily in the area.