My parents Want to get a Loan for land. it is under 50k but despite my father having decent credit( they require over 700 for all 3 scores and 1 of his is over 700 while the others are high 600's) they denied him the loan.

Unknown tenants abuse floors.

Setting aside the fact that 1000's and 100's of people abuse the FHA loan program for the purchase of single-family homes for investment purposes all the time, you should be proud that you did not and you achieved your goals on a much more solid financial footing by doing it the right way.

If you deny an applicant or take any adverse action (i.e. charge higher security deposit, require co-signer, etc) based on information in their consumer credit file, then you should be sending them an adverse action letter which basically tells them what consumer reporting agency supplied the info you relied on, the contact info for that agency, and how they can get a free copy of their own credit report. 

No need to replace as it is a great product that will last tenants abuse.

Call an exterminator as a courtesy one time, better have happy and long term tenants, then abusive short term tenants, give it another chance, do not panic, just step by step.

A project on RI's coast required zone IV yet the state denied a permit based upon the Industrial Building Commission; the IBC board is comprised of modular home builders using wood and completely self-serving regulatory body.

So the reason for being denied is actually based on incorrect information.  

If they deny access, call the police.They may be lazy and unclean tenants, but you seem aware of this for a lengthy time period and allowed it to continue. 

I will definitely educate myself more on the sub to clauses, and I can certainly see how an investor could abuse a service to their favor monetarily.