Hi nicola b and welcome to the forum
If you are going to be sharing a property with your partner, you will be expected to contribute to the shared costs in the same proportion as your individual earnings - ie if your partner earns twice as much as you, they will need to pay twice as much towards the joint expenditure. I expect that your IP will want to see details of your partner's income and also the new household and living expenses you anticipate incurring. If this is done fairly, there is no way your partner can be deemed to be indirectly contributing towards your debts.
With regard to the house, you will need to ensure that the rental income at least covers the outgoing mortgage payments, and that any surplus is forwarded to your Supervisor by way of increased contributions.
There is no guarantee that your IVA will not affect the credit rating of your partner.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk