No its not a requirement..You can live here for up to 2 years on tourist visas..(leave the country for a day,come back and start over) To acquire a 13a the most important requirement is to be married to a Filipino citizen..You can apply in the UK or over here although better to apply in the UK.Medical ? is this a requirment to be able to live in philipines ?and is it done here or in philipines ?
There are another options for long term stay for those that are not married.. Google search 13b quota visa and SRRV which is a retirement visa for more info..
Obviously..If you are married and you enter the country with your spouse you can avail of the balikbayan stamp which allows you to stay for one year..Good thing is..Its free.
Cheers,
Fred.