Hi Shuvie,
Just so you know, whilst he is not able to claim any benefits/public funds once here on a spouse/fiance visa, you are required to submit a joint claim for tax credits. This is because whilst you alone are entitled to them, they have to take into account the fact he lives wiht you, and may earn a salary. You will not be given any extra tax credits as a result of him living with you, but you have to apply jointly, as to not advise them is a criminal offence. There is some good information regarding this in the Claiming Benefits section on a "sticky".
You need to be able to prove to the ECO that you can sponsor him financially, meaning that after your rent/mortgage, council tax and any loans, you need to have £105.95 left each week. This is the threshold that must be met. I do not know for sure whether they would refuse an application if you down by £7.00, but presumably the threshold is there for a reason.
If you are successful in a fiance visa then as you know he is unable to work, but he is able to switch to spouse visa from within the UK after the marriage. You may want to bear in mind the additional visa fee in doing this.
It is also a condition that your relationship is genuine and subsisting, and that the parties have met. The ECO needs to be completely convinced that this is a genuine relationship and see evidence of the same It is slightly concerning that you have never met him, yet know you want to get married to him. I don't mean to sound judgmental whatsoever, but I want you to be aware that ECO's are very cautious in scenarios siimilar to this. It might be beneficial for you to visit him a few times before marriage, keep flight tickets etc, have photos, meet his family, etc. All of this is evidence which will help to satisfy the ECO of your relationship.
Hope this helps a little and I hope you have a great time in Turkey!