I wouldn’t be worried about if you are allowed to buy it or not. You should be concerned with who you can sell it to. You may be limited to buyers with incomes between 80%-50% of county median income.
“Low income” is an income category within affordable housing language. There are usually three categories:
“Moderate income” = Typically, 120%-80% of county median income.
“Low income” = Typically, 80%-50% of county median income.
“Very low income” = Typically, under 50% of county median income.
You should check what your county’s income limits are for affordable housing. Search google for “affordable housing income limits (INSERT YOUR COUNTY HERE)”. You may find that the price you set for the condo will attract buyers in the “Low income” category if it was an affordable unit or not.
Why is their a deed restriction in the first place? Most cities and counties feel they don’t have enough supply of housing to attract lower income individuals. Think Marin County etc. So, they offer incentives to developers to include affordable units in their projects. Most cities and counties in northern California won’t approve a project unless there is an affordable component included.
The cities and counties (and state and feds) will assist developers in applying for special project financing if they include affordable units. Think bond financing. They will also do things like allow developers to build more units, forego various fees, and/or let them build less parking than is required.
All of the above is a back and forth negotiation between developer and the city/county. Sometimes a very aggressive negotiation as the developer may not want to build affordable units in the first place. Because of the negotiation process, the income limit deed restrictions may only last a couple years. Most of the time, the deed restrictions will last 25 years or more, but not always. Sometimes there are zero deed restrictions put in place.
(I have written all of this with the assumption that this isn’t simply a Section 8 rental.)