We bought the duplex after living here for five years, next door to our landlord, who was an extremely nice older woman, that we never had a single problem with, everything went smooth transitioning to renting the place after our old landlord moved out, but we feel that we have genuinely rented to the wrong people at this point.

There are gaps in several areas and at the butt joints.

Fortunately my wife had a joint account with her mom for many years and we showed them the bank account, and they accepted that.

@Michael GiuffreYou may want to look to see if you can add his name to the mortgage and title and operate the rental as "tenants in common" or "joint tenants with rights to survivorship".This will allow you to both report the income/expenses from the rental property.

Many businesses operate as sole proprietorship.The one thing to be concerned about is if the costs you spent last year were "start-up" expenses. if they are - you may need to accumulate them and expense/amortize them when you "start" the business.If you are in the rental real estate business - it won't necessarily matter whether the income is earned under your name or your wife's name since it will be reported on your joint tax return.If you are generating income that is subject to self-employment taxes(flipping or managing real estate); it may make a difference whether the business under your name or your wife's name.if under Wife's name - you may pay more overall self-employment taxes; however, she will be credited with social security being paid in.If you are unhappy with your CPA - There are many CPA's on BP who work with real estate investors remotely. 

To qualify for a larger property we'll need to use my income but the property is solely in her name (deed and mortgage) and due to 1031 rules it's unclear if I'll be able to get added to the replacement property.We've been filing taxes jointly for 4 years and some people I've talked to have said that's enough to make this work.Does anyone have any experience with this or know of anyone/resources in Massachusetts?

I'd want every tenant on the lease, and "joint and severally" liable. 

Pair all of this caution with being kind and genuine and I think you will do just fine.

I would give you my sponsor's contact info, but they no longer do TICs or joint ventures.Good Luck and beware of BP posters that tell you how great DST's are...

The intent is to eliminate any potential deflection is the floor which would transition through as cracks in your mortar joints and/or tile.