How big is market for replacement doors

[voltarol]

How can anyone on here answer those questions,we have no idea what your running costs will be let alone how much business you are likely to get,and what you consider a modest income,if I knew it would work I would re mortgage my house,bombard the place with advertising and let the money come in,but I don't know so I just limp along doing what I'm doing,the answers you have had so far are probably as good as you can expect,good luck with your venture if you do decide to go ahead