Depending where the sewer and water lines run, live roots can cause issues for pipes and foundations.Healthy old-growth is often attractive.

Most of them leave the places reasonable clean, or not too messy.The lady that cleans my STRs used to do it for free. 

They are rented out 5-9 months out of the year.A lady I know cleans and stocks them between vacancies, but that is another story.

They set the opening bid so low to attract attention.

Not suggesting this will be the outcome in every instance, but concur with others that you may want to consider holding if the other aspects / fundamentals of your market remain attractive.

Take pictures of units, design flyers and bring flyers of vacant properties to local businesses to attract more and better tenants.I'm now looking for multi family buildings with 5+ units which would grow my portfolio exponentially and further create the need for a full time Property manager. 

If buying older properties im thinking one may be able to buy way more than properties build post 2000 but wondering how desirable older properties are and if not so desirable perhaps lower income people are attracted to these?

Its the Entitlement mentality,   Me , Me, and only Me counts.I notice several threads where the new woman landlord comes on here saying the tenant is ANNOYING(keyword)  when the tenant isn't that.Wait till the tenant calls with a plugged up toilet amd this lady has to plunge a toilet full of D.i.a.r..h.e.a.Wait till this lady is texted by a former tenant to give back security deposit or family will be OFFED.These women need a good ole Wake-Up call.It's not just young women.

yes, I changed cleaning ladies 3 times in 6 months until I found one who will check all these details.  

Couple that with the convenient access to NYC and it makes for an attractive alternative for many young couples and first time home buyers.