Praise be to Allaah.
Firstly:
It is not
permissible to put money in riba-based banks unless that is essential in
order to protect it, so long as that is without interest. See the answers to
questions no. 23346,
22392 and
49677.
Secondly:
If one full
year has passed since you acquired the nisaab (minimum threshold) then
zakaah must be paid immediately, and it is not permissible to delay it
beyond that when one is able to pay. A person does not have the choice of
selecting a particular month for paying zakaah on his wealth, rather that
month should be after one year has passed, unless he is paying it in advance
in Ramadaan, before the year has passed, in which case there is nothing
wrong with it. But after the year has passed, it is not permissible to delay
it until Ramadaan.
See the
answer to question no. 26716
and 8400.
Thirdly:
If you pay
zakaah on all your wealth, even your monthly salary, this is safer and is
the easiest way of paying zakaah on what you have saved of your salary.
See the
answer to question no. 26113
and 50801.
Fourthly:
We have
already explained that riba (usury) is haraam, and it is haraam with regard
to building and buying houses. If that loan is riba-based, then you must
hasten to repent and get rid of it, seeking that which is with Allaah and
fearing His punishment.
See the
answer to question no. 45951,
21914,
22905
Fifthly:
With regard
to the zakaah of one who is in debt, the correct scholarly view is that the
debt cannot be subtracted from the wealth on which zakaah is due. In the
example which you mention, you have to pay zakaah on the full one hundred
thousand, and you cannot subtract from it the debt that you owe.
See the
answer to question no. 65763,
22449 and
22426.
And Allaah
knows best.