Wife/Husband - who should buy houses

[Anthony Charles]

I am going to purchase two investment houses (single-family homes, SFH) this summer, and would like to do another two next year.

I need advice on whose name to title the property, and how to proceed with the mortgages.

Here's the situation

House A (my primary residence)
House B (wife's primary residence; she also rents to a roommate)

We just got married, about a year ago, and because of school & jobs will likely be separated for a bit longer. House A & B are in different states.

House C (investment property - SFH)
House D (investment property - SFH)

We are purchasing these this summer. The houses are located directly next to one another.

Currently, I have qualified for the mortgages b/c my wife is still in school and therefore has no material income (~15k/year).

Both of us have very good credit scores, but her income poses problems when it comes time to get a mortgage.

My current intention is to have the mortgage in my name, and the title of the properties in both our names.

However, next year we would like to purchase another two houses.

House E (investment property - SFH)
House F (investment property - SFH)

My concern is that there seems to be some rule, or difficulty, in securing more than 4-mortgages in the same persons name.

How does this rule work - does it only depend on the mortgage? Or does it matter whose name is on the title?

How should I get these the mortgages and titles of these investment properties? Both this year, so I don't create a problem in the future, and next year.

Somewhat related - am I going to run into a problem next year b/c 2-years of rental income on the tax return are needed in order for them to count?

Also, if we file jointly (taxes) - who does the rental income count towards? For example, next year will I be able to count my wife's roommate rental income on my loan application for the new houses?

Any advice would be appreciated.