present tense 
  
 they sell houses 
 Houses are sold by them

 past tense 

they sold houses
  Houses were sold by them

  present continuos

they are selling houses
Houses are being sold by them

 past continuos

they were selling houses
Houses were being sold by them 

 future will

they will sell houses
Houses will be sold by them 

 future going to 

they are going to sell houses
Houses are going to  be sold by them

 present perfect

they have sold houses
Houses have been sold by them

 past perfect

they had sold houses
Houses had been sold by them 

irregular verbs on PhotoPeach

 explanation of should and shouldn't

      should

       He should work harder

you should see a doctor 

should i talk to hear

shouldn't

 you shouldn't go to the dentist's

We shouldn't arrive late

personality on PhotoPeach