How long does an I-130 take to be approved?

It depends on the preference category in which the I-130 was filed.

About 6-8 months.

The processing time of Form I-130 petition will depend on the category of each particular petition. For example, a stand alone I-130 petition for immediate relative of US a citizen is usually approved within 8 months or so of filing, since such petition is not subject to any category or limit. In fact, such I-130 petition when filed concurrently with an I-485 adjustment of status application, it may be approved even more quickly (4-6 months). Conversely, petitions by green card holders for immediate relatives and even petitions by US citizens for their non-immediate relatives, because they are subject to cap and limits will take much longer time to be approved. Such petitions have historically been subject to caps and limits. And, for optimal utilization of its scarce resources, DHS will not devote its energies to these petitions until such a time when visas under that category are expected to become current. The length of time it will take to adjudicate your own petition therefore depends on your category. You should check the state.gov web site periodically to get an assessment of how long your own petition will be approved

It depends on the family relationship. Spouse is about 2-8 months. All others can range from 3 months to 5-10 years.