Or do I need a specific software to obtain this info? 

Buildium is not appropriate software for short-term.

First, it is a good idea to have a mini-application ready to store any information.

This company is a scam, they have mediocre software and zero support.

The right lender will be able to advise you on what options you have after getting some info from you and taking an application. 

Quote from @Emily Mohr: Software is a common question on BiggerPockets.

Pay for 2 hours consultation time from an attorney experienced in contractor real property law (if you don’t know of an attorney contact me and I will provide a referral) to understand the specific applicable laws, the risks, and potential costs2.

In some cases, exemptions or adjustments might apply for buyouts between co-owners, so it’s best to check directly with a local real estate attorney or tax advisor to confirm the exact tax amount and any applicable exemptions.

The standard to apply is quite simple: Did you accurately disclose the character of the down payment funds to the lender in the loan application?

Google search gives me these super wide ranges and mostly talking about adding a bedroom in a SFH, which I'm not sure if applicable to this situation of "moving/subtracting a bedroom from one unit and add it to another unit in a duplex".