Stuck with rent control

[Chen WU]

I am in California and found some properties with tenant occupied for sale. The numbers could potentially work except the fact that current tenants have been living there for 10+ years and rents are way below fair market rent (some units are less than half the market rent). One tenant is over 60 years old, who said he has been living there for 30+ years and had several different landlords. And seems like senior renters are protected by the state and probably the tenant is emotionally tied to the property. If I buy the property, it'd be difficult for me to raise rent and will probably be stuck with the low rent for another 10+ years. Plus the house is very old and will definitely need some work when they move out but it has great potential (a nearby house after renovation sold for double the listing price of this one) 

One strategy is to make the offer based on the monthly income accounting for the maintenance and capital expense (probably no need to consider vacancy, otherwise I can renovate and raise the rent) . That way, it offer price would be way below listing price (~70%).  Is it worth a try and the risk? Thank you in advance.