With a lease option you could negotiate for some of the rent to be applied to the purchase price, but you might pay a higher rent for that right.

After the year is up, and your primary postal address hasn't changed throughout, what can anyone then say, if you wish to change your primary address and apply for a new loan then? 

where do I look for the best rates and when applying how do they know if it’s tied to a 504

Keep that in mind as it probably applies to most small models. 

An additional requirement that may also apply to those mentioned above is if the reason used for the 2nd fha loan is due to an increase in family size/existing property doesn't meet family needs is having a 75% LTV on the existing property with the fha loan or paid down to that amount, based on the existing loan amount and an appraisal

At least for my properties (STR houses), the maintenance expenses are not even $200 a month:Lawn maintenance: $60-75Pest control: $30Pool (which I don't know if it would apply to your property): $65-90 dependingHVAC maintenance: $70 every 6 months (~15 a month)Capex of $3,000 a year means a bunch of appliances are breaking down continuously, or the house is in dire conditions.

Sacramento landlords, I just saw this:Emergency rental assistance program in SacramentoIf you have low-income tenants who aren’t paying rent due to COVID, you might encourage them to apply for this.

I am a firm believer in time-in-market > timing-the-market, but that notion really only applies to long run strategies.

When applying for a mortgage will there be a difference if I let the mortgage lender know it’s for short term rental investment or is it better not to inform that ?

I'm less concerned with specifics by state at the moment also and more interested in hearing what others are doing that might directly or indirectly apply.