heavily1121

Foreigners can purchase property.  However, I don't think it gives them any special benefits.  

B2 visa is required if your parents want to visit longer than 90 days.  The general rule of thumb for visits is twice as long outside of the US than in.  So, for a 5 month visit, your parents should travel back and not return until 10 months later.  This is just a guideline.   
 
Ultimately, It is up to CBP to allow entry and set the duration.  They need to be satisfied that your parents are just visiting and are not a risk for overstay. 

Had loads of issues with IRS when filing for my first year of taxes in the US. Whole tax system is here is so unnecessarily complicated and difficult to understand, and then the pandemic greatly affected the processing of our paper return for 2019 taxes.
 
With Skatteverket, however, it was unexpectedly smooth sailing. After moving, I mailed in form SKV 7665 (https://www.skatteverket.se/privat/folkbokforing/flyttautomlands.4.18e1b10334ebe8bc80001591.html). Although I wasn’t registered as utvandrad until a couple of months later, haven’t had any issues filing Swedish tax returns with zero Swedish income. My address is shown as the US address on transcripts/other papers from Skatteverket. Only thing is of course that when visiting Sweden, we are no longer entitled to healthcare benefits, so travel insurance is a must in case of any trips to ER (I seem to be particularly injury-prone…).

I'm not sure how much you earn but you can only exclude a certain amount per year  ($107, 600 for the 2020 tax year). It should go up for 2021. The tax year also runs from January 1 to December 31 so if you enter the States in 2021 to activate your card and continue to work in Sweden into 2022, you'll have to file the 2555 for tax years 2021 AND 2022.
To qualify for the FEIE you'll either use a physical  test or BONAFIDE resident test. The physical presence test is where you have to be in Sweden for 330 days in 12 months (and this doesn't have to start in January and end in December) so you unless you stay in the States for more than 36 days when you activate your residency you should be okay. 

Always refer to IRS site for best info
 
BAsically can be left up to you if u file using form 2555 for exculsion of us taxes as you pay in Sweden
 
https://www.irs.gov/pub/int_practice_units/JTO9431_01_02.pdf
under other considerations that impact 
 
TREATY IMPLICATION: An LPR may be a tax resident of both the U.S. and a country with which the United States has an income tax treaty (sometimes referred to as a “dual-resident” taxpayer). If so, the individual might be eligible to be treated as a resident of the other country under the residency “tiebreaker” rules of the treaty with respect to that taxable year (or portion thereof) during which the person was considered a dual-resident taxpayer. A dual-resident taxpayer may also elect not to be treated as a nonresident alien by not claiming treatment as a resident of a treaty country under the residency rules of an income tax treaty and continuing to file returns as a resident alien, i.e., Form 1040.
 
If u are coming under spouse visa ,  u will have a SS # and do need to file as MFJ or MFS
no timeline so no status to know if a spouse needs to file but if u come and return this year spouse would follow the IRS for nonresdient alien spouse for work outside the US for the entire year married 
 
 https://www.irs.gov/individuals/international-taxpayers/nonresident-aliens
 
 
Please do a timeline,  it helps 

VWP is limited to 90 days, would need a B to stay 4 to 5 months.