Getting a second mortgage for self build

My husband and I have been gifted a site, it's value in the region of about 30k

We currently have a tracker mortgage we've been paying for the past 6 years, monthly repayments are €650. We had saved 20k deposit for this house. 160k left on this mortgage.

We are now considering building a home on this site my husband has been gifted. We would need a mortgage of 200k but we want to keep existing house as an investment. We have the option of moving into another house and paying minimal rent and renting out our house getting in the region of €550 per month in rent.

Husband Salary €36,000
My Salary 19,750 (I work part time 3 days per week)
Monthly costs not including mortgage would be €750 includes creche fees for our only child and a car loan with CU.
Savings 25k

What are our chances of getting a second mortgage? Or what should we start doing now to help us get into a good position to apply for a second mortgage.

Thanks in advance

When you say "self build", do you really mean appointing a builder yourself to carry out the build?
There are new Building Control Regulations in place currently which effectively put a stop to the traditional self build process.

Based on the above figures, I think you will struggle tbh.

Get out of existing house. Get the rental income started as the banks will allow a % of this onto your income.

Are your crèche fees on the bank statements? Can you pay them cash directly?
I don't know if the banks can see your credit union loans at present, some say they can, some say they can't, I know when I was in with PTSB last October chasing our second mortgage they couldn't see it.

Most you will be able to borrow is 80% of the value of site and cost of construction = 184k so will need savings of 16k. You do not give enough information to be able to advise if you would qualify for 184k such as value of existing property, what is tracker interest rate, term outstanding, how much savings do you have, what ages are you, how much you owe credit union and monthly repayment and how much is crèche fees. I think you should try and pay off credit union. It may be a better idea to sell your existing property and perhaps move your tracker to the new mortgage which will also depend on your existing lender.