An actual college would have a typical offer of 5 GCSEs, but they often aren’t bothered if you have a valid reason for taking less exams. If you have studied the subjects you want to take up to GCSE level, but haven’t taken all the exams for financial reasons, they might accept your maths and English grades as evidence you’re at the right academic level to start A levels.
For example, if you had in 8 in GCSE maths, that would be clear evidence you were at an appropriate level to start A level maths. A high grade in English would be evidence you could start English A level, and probably some other essay subjects too. You would probably struggle to convince them if you wanted to take science subjects without any GCSE science exams though.
What subjects are you thinking of taking at A level?