Moving From My Main Residence Into Investment Property. What Are The Pitfalls?

I am currently trying to rent out my main residence but so far little interest.

I am in the process of moving into an investment property I have, as the mortgage is more affordable.

I am currently paying an agreed amount of money off my main mortgage each month; subsequently the bank have ceased passing on my mortgage interest relief.

I am concerned that when I apply for social welfare from the investment property address that the main residence mortgage provider will be informed and hence will lead to problems.

I am also terrified that when the bank hears I am claiming social welfare . . .

Any advise more than greatful.