As eileenf said above, LINC assessment is not an approved language proof.
Still you can go for LINC assessment which is free at YMCA, if you are limited on budgets; then you have to attend at least two months classrooms sessions (again free) in any approved community/training centers to get the certificate. YMCA do arrange enrollment. The certificate is valid for next six months, i.e. you have to apply within six months.
You may have to wait for few weeks/months to get a seat in training centers depending on your status i.e. single/childcare requirements.
If your pocket is thick enough; there are other options to go which costs around min $150- 200, by taking any of the following third party tests.
See below link for more info:
http://www.cic.gc.ca/english/helpcentre/answer.asp?q=572&t=5
What third-party language tests will CIC accept as proof I have adequate knowledge of English or French when I apply for citizenship?
A third-party test is a test done by an organization that is not CIC.
We will accept third-party test results as proof of your language ability if it is from one of the following organizations:
CELPIP General (Canadian English Language Proficiency Index Program General test)
CELPIP General-LS - a two-skills (listening and speaking) version of the CELPIP General test
IELTS - General training - General training (International English Language Testing System)
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We will not accept third-party test results that are not on this list, even if they are similar.