Thinking about buying cheaper house - what happens to mortgage?

Hi All
I bought my house as a FTB 3 years ago and am now thinking of moving to a cheaper house in the midlands (currently in Wicklow). The house I would be looking at would be about 100k cheaper than the mortgage that we have owing on our existing house. What sort of implications does this have? Obviously I know my mortgage monthly payments would go down, but would it be the same mortgage or would I pay off the existing mortgage first (assuming I get that amount when i go to sell it). And then take out a new mortgage for the new house?? Sorry if this sounds really stupid but its all so new to me really.

Its all pie in the sky at the moment but if I could get some clarity in my head it will make thinking about it a bit easier!
Thanks in advance

Steps:

1. Sell your house.
2. Pay off your mortgage.
3. If you have any clear equity ( the cash you are left with after you sell your house) do your sums. How much is new house? How will you pay for it?
4. If you have not enough ready cash, then you will need a new mortgage to buy the second house.
5. Will anyone lend you the money to buy the new house?

It really is a simple calculation. Unfortunately, houses are not selling at the moment and many banks are not lending. So you may well find that what you would like to do is just not feasible.

mf

Mf1 thanks a mill for your reply. Ive checked into the o/s amt on our mortgage and (being realisitc) I think it would be near impossible to get that amount in the current market for our house, meaning, we are in negative equity

So Im presuming therefore that we can really even sell our current house? If we did we would still owe around 15k to the mortage. Unless we could put that 15k onto the mortgage for the new house we were thinking about? Not sure if that would be allowed though.

Thanks again for replying its not looking good for us to be able to move at the moment!